A SECTION D. 



sometimes even a minor character appears to be constant, and 

 affords a pretty sure clue to the identification of a species, in other 

 cases characters that in most plants would be considered of the 

 greatest importance will be found unreliable in Eucalypts. Thus 

 it is also with the bark, which, though generally such a good 

 guide, varies in some instances to a remarkable degree. This is 

 well exemplified by Eucalyptus viminalis ; this tree, which grows 

 around the Melbourne herbarium building, shows here, in its 

 sapling state, a smooth, whitish bark, until it attains a diameter 

 of from 4 to 6 inches, then gradually the outer layers remain 

 attached, at first near the base only, becoming rough and brown ; 

 as the plant gets older, these layers creep higher and higher up 

 the stem, until, in aged trees, the whole of the trunk and also the 

 larger branches are covered with a thick, rugged, dark brown bark. 

 Within 10 miles inland from Melbourne, already the tree changes 

 its character in this respect, inasmuch as only the lower part of 

 the stem is covered with this rugged bark, while another 10 miles 

 further towards the ranges, this species presents a smooth, white 

 trunk, except, perhaps, just near the ground. Although the 

 floral characters remain the same, yet, any one seeing only the 

 two extreme forms would certainly consider them two distinct 

 species. Euc. leucoxylon shows similar anomalies. As another 

 instance of the difficulty of arriving at a correct limitation of the 

 species of Eucalyptus, I may mention the fact that Bentham 

 wrote that after he had finished his description of all the species 

 of this genus for the Flora Australiensis, he considered it neces- 

 sary to re-examine the whole of the collections, a thing which, for 

 want of time, he did not do with any other group of plants. There 

 is one feature which will, probably, throw more light upon the 

 limits of species as well as their affinities, with which we are not 

 yet sufficiently acquainted ; this is the character of the seedlings. 

 I venture to express a hope that in the near future one of our 

 botanic gardens will undertake the investigation of this subject, 

 which requires not only great knowledge and care, but also certain 

 means that are only at the command of few people. 

 . In submitting this contribution to Australian botany, I trust 

 that with all its shortcomings it will prove of some service in 

 identifying the species of our most important genus of timber trees. 



No. No. 



Calyx four-toothed ... ... ... ... ... 1 



Calyx truncate ... 2 



(No. 5, E. tetraptera shows an approach to a four-toothed 

 calyx.) 



1. Fruit fully J inch long, E. tetrodonta. 

 Fruit under J inch long, E. odontocarpa. 

 (Probably a variety of the above.) 



