Critical revision of the genus eucalyptus Volume 1: Parts 1-10

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Critical revision of the genus eucalyptus 
Volume 1: Parts 1-10 
   Maiden, J. H. (Joseph Henry) (1859-1925)  
   University of Sydney Library  
   Sydney, Australia 
   © University of Sydney Library. The texts and images are not to be used for 
commercial purposes without permission  
Source Text: 
   Prepared from the print edition of Parts 1-10 Critical revision of the genus 
eucalyptus, published by William Applegate Gullick Sydney 1909. 349pp.  
   All quotation marks are retained as data.  
   First Published: 1909  
583.42 Australian Etext Collections at botany prose nonfiction 1890-1909  
   Critical revision of the genus eucalyptus volume 1 (Government Botanist of New 
South Wales and Director of the Botanic Gardens, Sydney)  
“Ages are spent in collecting materials, ages more in separating and combining them. Even 
when a system has been formed, there is still something to add, to alter, or to reject. Every 
generation enjoys the use of a vast hoard bequeathed to it by antiquity, and transmits that 
hoard, augmented by fresh acquisitions, to future ages. In these pursuits, therefore, the first 
speculators lie under great disadvantages, and, even when they fail, are entitled to praise.” 
   Macaulay's “Essay on Milton” 

   William Applegate Gullick, Government Printer  

   DURING the twenty years that have elapsed since the publication of Mueller's 
“Eucalyptographia,” which added valuable information to Bentham's masterly account of 
the genus Eucalyptus in the Flora Australiensis, we have obtained a large accession of facts. 
It seems to me that the time has arrived when these additional facts should be incorporated 
with the labours of the old workers. I have spared neither time nor expense to obtain access 
to the types. I have spent many years in field observations on the genus in every State of the 
Commonwealth (though of course particularly in my own State of New South Wales), and 
thus have endeavoured to secure what is an essential qualification for the study of this 
protean genus.  
   The admirable illustrations contained in the “Eucalyptographia” have the defect that it is 
not always possible to say precisely what they depict—that is to say, whether a type or co-
type, or, if neither, the exact locality whence the originals were obtained. In all cases I shall 
inform my readers as to the history of the specimens depicted.  
   A very important departure in a work of this kind is the following:—While expressing my 
opinions as to affinities, synonyms, &c., I shall in all cases give the original descriptions of 
the species whether considered to be synonyms or not. In this way my readers will be able 
to weigh the evidence for themselves, and, if they do not concur in my conclusions, they 
will at least be placed in possession of the data on which they are based.  
   The genus Eucalyptus is the most important in Australia. The individuals which comprise 
it are all pervading, while the number of species and varieties is very large. As the work 
proceeds I will give my views as to the grouping of the species.  
   The present part contains much prefatory matter referring to the genus. Then one species 
is taken in detail, and the other species will be treated in a like manner, the facts being 
grouped in the same way.  
   The rapidity with which this work can be issued depends mainly on the plates; I have only 
the partial services of one artist.  
   Botanic Gardens, Sydney,  
      January, 1903.  

Part I 
Critical Revision of the Genus Eucalyptus Part I 
   J. H. Maiden 

A Critical Revision of the Genus Eucalyptus. 
A.—Variation in the Genus. 
   THE genus Eucalyptus is such a large one that a number of schemes have been 
submitted for dividing it into sections with a view of associating those closely 
allied, or for arriving at the name of a species with facility. These schemes will be 
referred to in the bibliography, and I now propose to review each character, from 
timber to another, to see if any satisfactory scheme can be evolved. In the Proc. 
Aust. Assoc. for Adv. of Science, Sydney Meeting, 1898, Professor Tate
 and Mr. 
Luehmann  simultaneously gave prominence to the use of the fruit for purposes of 
classification. Both papers take cognizance of other characters as well. Both are the 
work of men who know the genus, and are valuable contributions to knowledge.  
   Habit.—Tate defines two habits of growth, viz:—Trees, and shrubby, stocky 
trees, to which he applies the vernacular names of gums and mallees, names well 
understood in Australia. He points out that in young plants of the genus there is a 
large inflation of the base of the stem, either at the surface or just below the surface 
of the soil. In gums (E. rostrata, leucoxylon, viminalis, &c.) this is eventually 
outgrown; but in the mallees (incrassata, uncinata, &c.) it persists and increases in 
size proportionately with the development of the branches which are emitted from 
it—in the mallee this rudely globose bole is partly subterranean. “The umbrella-like 
disposition of the foliage of the taller mallees may be largely incidental to 
overcrowding, though it would seem to be an inherited character, as it is fairly 
pronounced in them when they are distinctly separated from one another.” This 
classification is chiefly of practical use in Professor Tate's own State (South 
Australia) and in Western Australia.  
   It  is,  however,  very  difficult to group the species according to habit. Some are 
dwarf in their typical forms, but under different circumstances they take on a larger 
growth. Then, speaking generally, such species as are found in damp situations in 
good soil are umbrageous trees; such, for example, are stellulaat, aggregata, 
Macarthuri, but this character is largely a matter of environment. Then some 
species, e.g., viminalis, have a more or less drooping habit as a rule, but this species 
is often nearly erect in less congenial soil. And further, to show variation in habit, 
we have only to point to the Eucalyptus plantations of California and the South of 
France, where the species are cultivated almost out of recognition.  
   Bark.—Mueller (Journ. Linn. Soc., iii, 99, 1858) arranged the genus in the 
following six groups in respect to their barks. With the additional information we 

have obtained since Mueller's paper was published, we are able to recast his list of 
examples. It will be found, however, that no two botanists agree as to the sections in 
which to place some of the species, and as further field-knowledge is available and 
we know more about the variation of the bark in the same species, the same 
authority modifies his own lists. See Woolls, “On the classification of the 
Eucalypts” (Proc. Linn. Soc. N.S.W. (2), vi, 60).  
   “i.  Leiophloioe.—Cortex post delapsum strati supremi undique laevis. (Vulgo, 
flooded gum trees, white gum trees, blue gum trees partim, red gum trees partim, 
yarra trees.)”  
   Smooth  barks  (“gums”  we call them).—Examples are—E. hoemastoma, 
tereticornis, rostrata, leucoxylon, viminalis, Gunnii, maculata, latifolia, aspera, 
stellulata, coriacea, saligna, Behriana, punctata, stricta, fasciculosa.  
   “ii. Hemiphloioe.—Cortex in trunci parte inferiore persistens rugosus et rimosus, 
in parte superiore ramisque delapsu strati superioris laevigatus. (Vulgo, Moreton 
Bay ash, blackbutted gum tree, box trees partim.)”  
   Half barks, the barks of the lower part of the trunk persistent and the upper part 
smooth. Examples are—E. hemiphloia, pilularis, bicolor, longifolia, melliodora, 
amygdalina, dives. The Moreton Bay Ash (tesselaris) is better in section iii or vi.  
   “iii.  Rhytiphloioe.—Cortex ubique persistens rugosus et rimosus intus solidus. 
(Vulgo, bloodwood trees, box trees partim, peppermint trees partim.)”  
   With wrinkled persistent bark, rather solid. This is an unsatisfactory group, 
including heterogenous barks. Mueller intended it to include the bloodwoods 
(corymbosa, eximia, trachyphloia), also bicolor  (which  is  better  in  ii)  and  E. 
microtheca, leptophleba, ferruginea. Odorata, robusta, botryoides may be added, 
and also Stuartiana, pulverulenta, microcorys, acmenioides, resinifera, 
polyanthema, populifolia, piperita.  
   Nos. ii and iii run into each other, and both of them into No. iv.  
   “iv.  Pachyphloioe.—Cortex ubique persistens rugosus intus fibrosus. (Vulgo, 
stringybark trees.)”  
   “Stringybarks,”  with  persistent, fibrous barks. A good natural group, including 
eugenioides, capitellata, macrorrhyncha, obliqua, pilularis var. Muelleriana, 
   “v.  Schizophloioe.—Cortex ubique persistens profunde sulcatus intus solidus. 
(Vulgo, ironbark trees.)”  
   “Ironbarks,” with hard, deeply-furrowed barks. Perhaps the best of all the groups. 
Examples—E. siderophloia, paniculata, crebra, sideroxylon, melanophloia.  
   “vi.  Lepidophloioe.—Cortex saltem in trunco persistens lamellaris friabilis. 
(Vulgo, melaleuca gum trees, mica trees.)”

   With persistent bark on the trunk only, and forming scaly separate pieces. 
Mueller's examples are miniata (aurantiaca), phoenicea, peltata (melissiodora), to 
which I would add tesselaris. The Rev. Dr. Woolls (Proc. Linn. Soc. N.S.W., vi, 
709) ignores section vi, and it certainly cannot be separately maintained as a section.  
   The cortical classification separates trees that are closely allied, e.g., hemiphloia 
and  Baueriana, the first being a half bark, and the latter having rough bark to the 
branchlets. Similarly E. pilularis in its normal form has smooth branchlets, while its 
variety  Muelleriana has rough branchlets. It places in juxtaposition those that are 
not closely related, as will be observed from the examples given under each section. 
Prominent examples are:—  
(aE. paniculata, Sm., and E. fasciculosa, F.v.M.; and  
(b)  E. sideroxylon, A. Cunn., and E. leucoxylon, F.v.M., respectively, nearly alike in leaves, 
flowers, and fruits, but utterly dissimilar in bark and wood.  
   Absolute  anomalies  as  regards barks are those of ironbark for E. stellulata, 
Sieberiana, and viminalis;  a box-like bark for E. tereticornis, and observers will 
note many other anomalies within their own experience. At the same time, in careful 
hands, the bark is the most useful character the forester can employ.  
   Timber.—While the character of a timber is a matter of economic importance, its 
use in botanical diagnosis is very often overlooked. For many years I have insisted 
on the examination of the timber wherever possible, and recognition of this 
character has undoubtedly led to a better understanding of the genus.  
   Timbers can be classified in different ways, e.g., according to—  
(1.) Fissility.—Some are fissile, such as stringybarks (E. eugenioides), &c., Mountain ash (E. 
Sieberiana), Victorian blackbutt (E. regnans), &c. Others are short in the grain, such as many 
gums, snapping off like a carrot; while others are tough and interlocked, like boxes and 
(2.)  Colour.—In a lecture delivered in 1891 before the Sydney Architectural Association of 
New South Wales, I divided many of the Eucalyptus timbers into pale hardwoods, subdividing 
them into three groups—(a) Hard, interlocked; (b) Fissile; (c) Inferior, such as Gums; which is 
a useful practical classification. In my “Notes on the Commercial Timbers of New South 
Wales,” (1895), I submitted the classification—1. Ironbarks. 2. Pale hardwoods. 3. Red 
   1. Gums.—These timbers are short in the grain; dry to a brown or reddish colour; 
crack radially in drying; have many gum-veins; and, as a rule, lack durability. Their 

barks are smooth, and more or less ribbony. Examples—stellulata, coriacea, 
hoemastoma, viminalis, Gunnii. They connect with the “Boxes” (Bastard), and also 
with the smooth-barked members of the Jarrah group.  
   2.  Mallees.—Examples—oleosaBehrianaincrassata. This is a group based on 
geographical considerations. They are arid country species, and connect the “Gums” 
and “Red Boxes.”  
   3.  Ironbarks.—These are fully described in my “Notes on the Commercial 
Timbers of New South Wales.” They consist of—  
(aTrue Ironbarks, viz., paniculata, siderophloia, crebra, sideroxylon.  
(b)  Bastard Ironbarks.—Timbers very similar to ironbarks, but the barks belonging to the 
“Box” group. They include Boormani and affinis.  Melanophloia, and, perhaps, microtheca 
connect the two groups.  
   4. Boxes.—These are tough, interlocked timbers, usually with fibrous bark on the 
trunk, and may be subdivided into—  
(a)  Pale.—Examples—Hemiphloia, melliodora, Bosistoana, Baueriana, populifolia, 
quadrangulata, Cambagei, goniocalyx, tesselaris, leucoxylon, corynocalyx, globulus.  
(bRed.—Examples—bicolor, microtheca, polyanthema, odorata, fasciculosa.  
   These  two  groups  include some smooth barks or “Gums,” but their timbers are 
provisionally classified with the “Boxes.”  
(c)  Bastard.—Examples—Stuartiana, pulverulenta, Macarthuri, aggretata. The timber of (c
is inferior, and closely resembles that of the “Gums.”  
   5.  Stringybark Group.—This includes a number of fissile timbers that pass into 
each other, and may be subdivided as follows:—  
(a)  True Stringybarks.—Examples—eugenioides, macrorrhyncha, capitellata, obliqua, 
(b)  Blackbutts.—Examples—pilularis (which absolutely connects with the Stringybarks 
through its variety Muelleriana),  acmenioides. These are the most valuable timbers of the 
(cPeppermints.—Examples—amygdalina, regnans, dives, piperita. These timbers have gum-

veins, and are altogether inferior in quality.  
   Allied to these is the—  
   6. Mountain Ash Group.—Fissile timbers usually pale in colour, and with bark not 
so fibrous as the preceding. Examples—Sieberiana, Planchoniana, virgata and its 
varieties, Risdoni, cordata.  
   7. Tallow-wood and Spotted Gum.—microcorys and maculata (two valuable pale-
coloured timbers), sui-generis.  
   8.  Bloodwoods.—These have gum-veins, and are coarse-grained; corymbosa, is 
red, and eximia and trachyphloia, which are pale, connect with maculata.  
   9.  Jarrah Group.—Containing a number of heterogenous species, and which I 
name after the best-known member. Some have fibrous barks, others are smooth; 
but they are all deep-red, durable timbers. Examples—marginata, resinifera, 
diversicolor, propinqua, punctata, saligna, botryoides, robusta, tereticornis, 
rostrata, longifolia.  
   This group connects with the Red Boxes.  
   The  timber  of  the  same species varies a good deal according to the soil and 
situation, and our knowledge does not yet enable us to discriminate between some 
timbers not closely allied botanically. In other words, a man who professes to 
discriminate between all species of timber attempts the impossible.  
   Exudations.—In  Proc. Linn. Soc., N.S.W., 1890, I proposed examination of the 
kinos as an aid in the diagnosis of eucalypts, and I divided them into three groups 
according to their behaviour in water or alcohol (spirit).  
   1. Ruby Group.—Consisting of ruby-coloured kinos, soluble in water and alcohol 
in all proportions. Examples are—all Renantherae except microcorys.  
   2. Gummy Group.—Soluble in water, but insoluble in alcohol owing to the gum 
they contain. Examples—the ironbarks.  
   3. Turbid Group.—These kinos are soluble in hot water or hot alcohol, but deposit 
sediments on cooling. Examples—most of the Parallelantherae. This section, 
however, includes heterogeneous substances, and brings together species little 
allied. It is doubtless capable of further elaboration, but only serves to accentuate 
variation in the genus. Some kinos, e.g., E. maculata, are characteristic in 
appearance, having an olive-green colour; perhaps also that of E. corymbosa, of an 
intense, almost vermilion colour.  
   An  exudation  of  less  importance is that of Manna. A number of species exude 
saccharine substances from the leaves and, a very few, from the trunk. The list is 
being added to slowly, but in most cases the mannas are mere scientific curiosities, 
and of little value in a scheme of classification. They include viminalis, Gunnii, 

punctata, pulverulenta, Stuartiana.  
   Petiole.—D. McAlpine and J. R. Remfrey, in Trans. Roy. Soc. Vict., 1890, 
published a paper entitled, “The transverse sections of petioles of Eucalypts as aids 
in the determination of species.” The method of classification on the comparatively 
few experiments made is ingenious, but of little practical value to us for diagnosis, 
thousands of sections being required in order to obtain data for generalisation. The 
paper is, however, of more than ordinary value, and is well worthy of perusal.  
   Leaf.—(aSuckers. De Candolle (Prodromus, vol. iii, 1828), classified eucalypts 
according to the opposite or alternate character of the leaves, a character of special 
importance at that time, since species were often described from seedlings grown in 
pots. Field observations have, however, shown that all species have opposite leaves 
in at least an early stage. In seedlings this is best observed, but in many cases 
suckers show the character quite as well. In a few species, e.g., gamophylla, this 
opposite-leaved character persists through life. In many cases the young leaves are 
broad, and become alternate and narrower, with a lanceolate or falcate shape as 
maturity is reached. Often these young leaves are glaucous, becoming glabrous as 
growth proceeds. But there is a group in which the seedling and sucker leaves are 
narrow. Such species include amygdalina, pilularis, viminalis.  
   The list is, however, so incomplete that it is impossible at present to use them as a 
broad basis of classification. For diagnostic purposes, I personally use the shape of 
the young leaf wherever possible; it is an atavistic character, and data are 
accumulating by which we shall be in a better position to interpret it.  
   The difference between suckers and mature leaves has been studied in Europe for 
many years, although in Eucalyptus the systematic comparison of such forms is of 
comparatively recent data. It is of practical importance to the Australian forester, for 
the reason that the occurrence of these young or sucker leaves is so very frequent in 
the bush.  
   When a trunk is injured, new shoots make their appearance either from the “eyes” 
in the stem or from reserve buds of the branches and twigs, or by buds produced 
from the roots below the ground. The leaves of these shoots, or suckers, as they are 
called, differ very much from the stems or branches which have been broken, eaten, 
cut, or frozen off.  
   Instances of differences are given, and it is added:—  
   Hundreds of trees and shrubs might be mentioned in which there is a distinct 
difference between the foliage of the suckers and of the normal branches of the 
crown. (Kerner and Oliver, ii, 515–6.)  
   Nor has the description of species and varieties from suckers or seedling leaves 
been confined to writers on Eucalyptus:—  

   Gardeners and descriptive botanists have frequently determined and described 
mutilated plants as other species, hybrids, or varieties. They are neither the one nor 
the other. The peculiar appearance of the altered members, resulting from 
mutilation, is exactly determined before hand in each species; it is due to the 
specific constitution of the species, and thus is part of its being. It is not produced 
by the external influences which lead to the formation of the varieties, but is brought 
about by inherent necessity quite independent of the influence of climate and soil. 
(Op. cit., ii, 518.)  
   Practically all the researches on the anatomy of Eucalyptus leaves have been made 
on those of the readily available E. globulus, in which species both sucker and 
mature leaves are readily available. The most complete research is the masterly 
paper of G. Briosi.
 See also a study by H. Pocklington.   
   Then Henslow  says:—  
   The chief differences between the two forms of leaves I find to be as follows:—In 
the horizontal leaf the upper epidermis is composed of small cells, and there are no 
stomata. There is a palisade tissue of one layer of cells, with lax mesophyll below 
the lower epidermis. This latter has larger cells than the upper, and is provided with 
stomata. The pendulous leaf is a good deal thicker than the horizontal. Both 
epidermides are provided with a very dense cuticle, in which the stomata are deep-
seated. There are four rows of palisade cells on both sides, with a chlorophyllous 
mesophyll between them. The petiole is flattened so that the leaf can swing much in 
the same way as that of the poplar.  
   A useful paper by Dr. Albert Schneider

 speaks of the sucker (“dorsiventral”) 
leaves with palisade cells on the upper side and stomata on the under side only. The 
mature leaves, “isolateral leaves or phyllodes,” take a vertical position with the 
convex edge directed upward. The epidermis is alike on both sides. It will be 
observed that his results do not agree with those of Henslow;—evidence of 
variation. The anatomical characters of the leaves of Eucalyptus offer, however, 
much room for research. See “Stomata,” p. 8.  
   (b)  Cotyledon leaves.—The shape of the cotyledon leaves we know less about, 
and data are being collected. The work has been hindered because of the difficulty 
of obtaining seed from certain interesting forms. Mueller's Eucalyptographia and 
Lubbock's “A contribution to our knowledge of seedlings,” form the basis of our 
present available information on the subject.  
   Other characters of Eucalyptus leaves we require to know more about are their 
size, texture, and prominence of venation. They are minor characters, and some 
species present much variation in this respect.  
   (cVenation.—Messrs. Baker and Smith, in Proc. Roy. Soc. of N.S.W., 1901, have 

grouped certain Eucalyptus leaves into sections in regard to the disposition of their 
veins, pointing out that the oil-content of the leaves can in a measure be gauged 
from the venation. The suggestion is ingenious; but as the venation is, like other 
characters, variable within such large limits, the method will only be practically 
useful in the hands of experts.  
   (d)  Young stems.—Some eucalypts have marked quadrangular stems, e.g., 
globulus, Maideni, goniocalyx, quadrangulata, tetragona, and many others; but, as 
a rule, this quadrangular appearance, often well marked at an early stage of growth, 
passes away as growth proceeds.  
   (eEssential oil.—The perfume of Eucalyptus leaves is owing to the presence of 
an oil. It varies in different species in regard to both character and amount. In young 
it is commonly more abundant than in mature foliage, the high proportion of 
resinous matter in the former being, however, a drawback to distillation. In some 
cases the perfume is not easy to define, but the crushing of the fresh or even dried 
leaves in the warm hand has been used as a diagnostic character for many years. It 
affords a rough but ready test, which is always available and really valuable in 
skilled hands. Incidentally it may be mentioned that some few leaves, e.g., 
corymbosa, contain a substance allied to caoutchouc in their tissues, especially in 
their young state.  
   Some years ago, when Superintendent of Technical Education, I determined to 
ascertain whether this qualitative test of Eucalyptus odour was capable of leading up 
to further results. Accordingly I obtained samples of commercial Eucalyptus oils, 
and also watched their distillation in the country, but found, as a general rule, that 
the various kinds of leaves were not rigidly kept apart. I therefore resolved, with the 
advice of Dr. T. L. Bancroft, of Brisbane, and the active co-operation of Mr. Owen 
Blackett, C.E., of the Technical College, to erect a model still capable of holding 
large charges of leaves, and to distil only those leaves obtained by my own collector 
or through agencies which permitted their origin to be precisely checked from a 
botanical point of view. In this way, and in this way only, could Eucalyptus oils of 
many species, absolutely true to name, be obtained for research. My transfer to the 
Botanic Gardens removed me from this domain of botanical technology, and the 
work thus initiated has been continued and extended by my late assistants, Messrs. 
Baker and Smith.  
   (f)  Stomata.—Mueller, in Eucalyptographia, under E. pachyphylla and E. 
phoenicea, has classified some of the eucalypts according to the number and 
distribution of the stomata. He styles the leaves—  

1. Hypogenous, according to the presence of stomata on the under surface only.  
2. Heterogenous, according to their presence on both surfaces, but less numerous above than 
3.  Isogenous, when they are present on both surfaces, but approximately equal in number 
above and below. “This almost equal distillation of the stomata coincides with the similarity of 
the colour of both sides of the leaves.”  
   This method cannot, however, be used for diagnostic purposes with any degree of 
certainty, because of the variation in the distribution of stomata even in the same 
   Galls.—At one time I inclined to the opinion that the shapes of the leaf-galls in 
Eucalyptus would be a useful character for classification. Mr. W. W. Froggatt, who 
has of late years been giving special attention to Brachyscelidae, finds that the same 
insect frequents so many species that no general grouping of the trees based on their 
galls can be made.  
   Inflorescence.—Professor Tate points out that the usual form of inflorescence is 
an umbel which, by lengthening of the axis, passes to the panicle or corymb. The 
transition from one to the other is so easy, he goes on to remark, and often 
exemplified in the same tree, that it is obvious the form of the inflorescence is not 
reliable as a specific character. Bentham had previously drawn attention to the 
unsatisfactory character of the arrangement of the inflorescence from the point of 
view of the systematist. Naudin's grouping (second memoir) of fifty-six species (or 
reputed species) known to him as growing in the gardens of Provence, is mainly 
based on the inflorescence, but also depends on the fruits and leaves. It doubtless 
was of local value, but it is based on characters which present so much variation as 
to preclude its general application.  
   Following is an abstract in Gardeners' Chronicle, 7th February, 1891:—  
      Section I.—Inflorescence in cymes or axillary umbels.  
         Capsules longer than the calyx tube.  
         Capsules shorter than the calyx tube.  
(a) Cymes 3-flowered. 
Leaves uniform, opposite.  
Leaves uniform, alternate.  
Leaves of two shapes.  
(b) Cymes of 3 to 7 or more flowered. Cymes 7-flowered. 

Leaves uniform opposite.  
Leaves of two shapes, opposite at first.  
Leaves uniform, always alternate.  
(c) Cymes or umbels, axillary, more than 7-flowered. 
Leaves uniform.  
Leaves of two shapes.  
      Section II.—Flowers in terminal panicles or corymbs.  
   Flowers.—With reference to individual flowers, there is much variation in the 
number of flowers in an umbel, and, to a less extent, in the colour of their filaments. 
The colour in the vast majority of species is white or cream, but in a few species, 
e.g., leucoxylon, sideroxylon, viminalis, ficifolia, calophylla, pyriformis, it may be 
pink also. In some species, e.g., ficifolia, miniata, phoenicea, it may be red, even a 
vermilion or orange-red. In a few species, e.g., pilularis, the filaments of dried 
flowers turn red in course of time.  
   The pedicel is normally rounded, but owing to compression it is very often strap-
shaped, as in botryoides, and extreme cases are afforded by obcordata (platypus) 
and occidentalis.  
   Flower-bud.—The shape of the operculum was first used as a classification 
character by Willdenow in his Species Plantarum, 1799. He divided the twelve 
species then known into two groups—“operculo conico” and “operculo 
hemisphaerico.” It is undoubtedly a useful character for the purpose, but variable, 
like everything else about Eucalyptus. E. tereticornis is usually looked upon as a 
species to be diagnosed by its operculum, but (Bull. Herb. Boissier, 1902, 579), I 
have shown that this character breaks down completely as between that species and 
E. rostrataE. capitellata and E. macrorrhyncha were at one time separated by their 
opercula, but they pass into each other as regards those organs. As this work 
progresses it will be obvious how very variable the operculum is. At the same time, 
it will always remain, in the hands of a judicious observer, one of the most 
practically useful diagnostic characters we have.  
   Some species possess a double operculum, or membranous bract, enveloping the 
whole of the young inflorescence. It was first observed by Robert Brown (see his 
description of Eudesmia tetragona), but a few years ago it was only recorded from a 
very few species. In some it is very early deciduous and in others infrequent; but I 
have observed it in such a large number of species that I am inclined to the opinion 
that extended research will show that it occurs in all. Brown's and Jussieu's 

interesting observations on the single and double operculum will be found 
supplementary to the former's description of Eudesmia tetragona (Bot. App. to 
Flinders' Voyage).  
   Anther.—Bentham (Flora Australiensis) first grouped species according to the 
shape and mode of dehiscence of the anthers. He made five groups, but laid no 
stress on the importance of the dehiscence on the top on the anther. He, however, 
alludes (B.Fl. iii, 186) to “truncate” anthers, and at page 189 to the truncate anthers 
of  E. leucoxylon. Mueller, finding that Bentham's five groups could not be 
separately maintained, reduced them to three, viz.:—  
   Renantheroe, the anthers large and the cells divergent at the base.  
   This section mostly includes the stringybarks, although it includes several white 
gums,—plants otherwise very different.  
   Porantheroe, the anthers small and opening in pores.  
   This section mostly includes boxes and some mallees, and includes the silver-
leaved ironbark (melanophloia), while E. crebra, which is very closely allied to it, is 
placed in another section.  
   Parallelantheroe, the cells parallel, and the longitudinal slits consequently 
   This section comprises the remainder of the eucalypts, and a most heterogeneous 
and extensive collection they are, variable in many ways.  
   As a matter of fact, the anthers refuse to be rigidly marshalled into sections. They 
sometimes display such variation of divergence of shape of cell, size, and mode of 
dehiscence, that classification on the anthers alone becomes a matter of difficulty.  
   In the old collections, the difficulty is enhanced through the partiality of insects 
for these organs; nevertheless, examination of the anthers is always carried out by 
me, and it is a most useful character.  
   Pollen-grains.—Mueller (Eucalyptographia, under E. erythrocorys) has shown 
that the size of pollen-grains varies in different species, but we require very many 
more measurements than are available, to be in a position to place any interpretation 
upon the results. The shape of the pollen-grains also varies, but we have few data on 
the subject.  
   Calyx.—The calyx, “cupula” of De Candolle and other botanists, the 
“hypanthium” of Schauer, is no longer used for classification purposes, having been 
proved to be so utterly variable. De Candolle (and his translator, G. Don) offered a 
classification of the eucalypts consisting of opposite or alternate leaves combined 
with a comparison of the size of operculum with cupula.  
   Fruit.—While many botanists have more or less used the fruit as a diagnostic 
character in Eucalyptus, and it is undoubtedly the best character we have, it is due to 

Professor Tate to say that (op. cit.) he was the first to submit a scheme for 
classification of the genus based on the fruits alone. He deals with (a) shape; (b
external sculpture and ornament; (c) capsular teeth; (d) capsule cells; (e) fertile 
seeds. But examination of Professor Tate's scheme shows (through no fault of his) 
how very imperfect and full of exceptions it is. Taking item by item we find the 
shape in each species to vary within wide limits. The truth of this will be observed 
in contemplation even of the single species, E. pilularis, dealt with in this part. 
Personally, I very largely use the fruit (unripe fruits may be very misleading) for 
diagnostic purposes; but in many cases it must be carefully used, for it displays an 
enormous amount of variation. This much is proved, and I go further and say that 
some fruits only appear to have an approximately constant shape because we have 
so much to learn in regard to the range of the species and consequent possibilities of 
variation. Of course, I at once admit the fact that some species are “stronger” than 
   To sum up, for herbarium work the anthers and fruits are the best characters to go 
by; for the scientific forester, the bark and the timber; but all characters display a 
puzzling amount of variation.  
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