PRESIDENTIAL ADDRESS. 41 



suckers or shoots from the roots, and a careful examin- 

 ation of the young growths which appear around and at 

 some little distance from a standing tree and look like true 

 suckers, results in the discovery that the plants are seed- 

 lings. 



Between these stem-shoot and seedling leaves there is a 

 great similarity, and as according to the general biological 

 belief it is in the young forms of both flora and fauna that 

 we may expect to find the greatest resemblance to ancestral 

 types, so we may regard these reversion shoots as of almost 

 equal value with the seedlings for the purpose of studying 

 the ancestral forms of Eucalypts. Although the leaves of 

 these "suckers" when available, are of considerable assist- 

 ance in the identification of many species, they vary within 

 certain limits both in size and shape, possibly in response 

 to differences of climate and to extremes of nourishment 

 and poverty. An interesting feature of their form is the 

 degree of dissimilarity between them and the mature leaves. 

 In some instances the difference is slight and in others 

 exceedingly great. Mr. Andrews has already pointed out 

 that the difference is greatest in the highland and coastal 

 region. 1 In addition to the disparity of shape and size 

 between juvenile and adult foliage, there is also a marked 

 difference in arrangement, with the exception of a com- 

 paratively few cases which thereby appear anomalous. In 

 the most diverse cases the juvenile leaves are sessile, 

 opposite and horizontal, orbicular to broadly ovate, and 

 perhaps covered with a glaucous bloom, while the adult 

 leaves on the same tree may be petiolate, alternate, vertical 

 lanceolate and glabrous. There are some species such as 

 E. dives and Risdoni, which flower while still in the 

 opposite leaved stage, but they eventually develop the 

 alternate lanceolate form. A Eucalypt with the adult 



1 This Journal, Vol. xliv, p. 467, (1910). 



