516 EVOLUTION OF THE EUCALYPTS, 



common thing, especially in the period from August to February, 

 for them to have prolonged times of quite severe drought, when 

 they get very little more rain than in the interior, and vegeta- 

 tion is severely tested thereby. Moreover, it is not uncommon, 

 in the lowlying coastal areas, to have hot westerly winds, raising 

 the temperature to well over lOO^F., and this would account for 

 the presence of such species as E. crebra and E. hemiphloia so 

 near the coast Attention has been drawn by various writers to 

 the fact that E. Smithii and E. microcorys are aberrant forms, 

 in that, while yielding a eucalyptol-pinene oil, they yet have 

 reniform anthers. The former, I find, has cotyledons of the 

 globuhis-type, while the primary leaves remind one a great deal 

 of those of E. amyydalina, and it may thus have a mixed ancestry. 

 The cotyledons of E. microcorys, in shape, have a good deal of 

 the " Peppermint "-type about them, but no purplish-red colora- 

 tion; while the primary leaves are smooth and petiolate, such as 

 we find in E. propinqua and other members of the group in 

 which I have placed it. It, too, probably has a mixed ancestry. 

 By reason of their yielding a piiiene oil and having a tiansverse 

 venation, Messrs. Baker and Smith placed E. botryoides, E. 

 robusta, and E. saliyna in the same chemical group as E. corym- 

 bosa, though, as regards the fruits and many other characters, 

 they have little in' common with it. The seedlings show that 

 they are far removed, as they all have emarginate cotyledons, 

 and smooth, petiolate leaves, and so have much more in common 

 with such species as E. resiiiifera. Apart from these exceptions, 

 almost the whole of these groups yield a eucalyptol-pinene oil, 

 and this is the oil most characteristically associated with the 

 emarginate cotyledons. A certain proportion also contain aro- 

 madendral, and some others phellandrene. E. Macai'thuri, with 

 its geranyl-acetate oil, belongs to the group with small cotyledons. 



Most interesting of all is the group with the emargination de- 

 veloped to such an extent, that they may be termed the Y-shaped 

 cotyledons. E. cornuta seems to connect, through E. gomphoce- 

 phala, with the globulus-type. ^ Species with this type of coty- 

 ledon seem to be most plentiful in Western Australia, and then 

 to have spread across South Australia to the dry interior of 



