471 

 COTYLEDONS 



(See Plates 286, 287). 



As might be expected in such a unique genus as the Eucalyptus, there is a fair 

 amount of diversity in the cotyledons, but the cotyledon is no exception to the general 

 rule that while two or more groups are more or less well defined, and therefore valuable for 

 classification purposes, the vast majority of intermediate ones are vague, and shade into 

 indefiniteness. The adoption of the cotyledon indicates at the outset a valuable 

 phytogenetic grouping, and indications of affinities, fundamental or more or less 

 superficial, will be brought out in the development of the key to the species. 



A study of the cotyledons brings together species which are very distinct from 

 each other in morphological characters, even in the sculpture and texture of the seed, 

 but possess similar cotyledons ; the only character in which they may be said to resemble 

 each other, as will be seen presently. 



The life-history of the Eucalyptus seedlings will be dealt with under " Seedlings," 

 which will appear in a subsequent Part, together with examples of seedlings, reproduced 

 by the ' : three-colour process." I may state briefly that I have classified the seedlings 

 into three divisions, according to the shape of their cotyledons, viz,. 



Reniformse ; Bilobse ; Bisectse. 



These are again subdivided into sections as follows : — 



Reniformce. 



(1) Large cotyledons; (2) Medium cotyledons: (3) Small cotyledons. 



The sections are further divided into series, and named after a well-known member 

 of the series or some outstanding character of the group or series. 



Reniformse is a large division, and some of its members possess the largest cotyle- 

 dons of the genus, as well as embracing a number of well-defined groups, viz., Bloodwoods, 

 Stringybarks, Blackbutts, Ashes, and some Gums, Mallees, Boxes, and two or three 

 small groups which are more or less closely allied to the Bloodwoods. 



Bilobce. 



This division is subdivided into twenty-six series. It is sometimes difficult to 

 draw a line between the Reniformse and the Bilobse, and it is idle to suggest that, in some 

 cases, one has not been biassed by a knowledge that the species is Renantherous or not. 

 Its members include Boxes, Ironbarks, Mallee-Boxes, White, Grey, and Blue Gums. 



Bisectee. 



This unique division is divided into fifteen series. Some of its members approach 

 the Bilobse, but broadly speaking, it seems to me to be the most well defined division of 

 the three. It includes nearly all the Mallees or Marlocks, and a number of dwarf species 

 which belong to regions of very low rainfall. It also embraces species with the largest 

 flowers and fruits of the genus. 

 D 



