524 - PROCEEDINGS OF 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 reexamine 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 sufliciently 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 aes uae ne we RA 1 
Calyx truncate ... sis was he ap ec 2 
(No. 5, H. tetraptera shows an approach to a four-toothed 
calyx.) 
1. Fruit fully } inch long, ZL. tetrodonta. 
Fruit under 4 inch long, #. odontocarpa. 
(Probably a variety of the above.) 
