Latent Characters 217 



The primary leaves, following the seed-leaves, 

 are different in many species from the later 

 ones, and the difference is extremely pro- 

 nounced in some cases of reduction. Often, 

 when leaves are lacking in the adult plant, be- 

 ing replaced by flattened stalks as in the case 

 of the acacias, or by thorns, or green stems and 

 twigs as in the prickly broom or JJlex europaeus, 

 the first leaves of the young plant may be more 

 highly differentiated, being pinnate in the first 

 case and bearing three leaflets in the second in- 

 stance. This curious behavior which is very 

 common, brings the plants, when young, nearer 

 to their allies than in the adult state, and mani- 

 festly implies that the more perfect state of 

 the leaves is latent throughout the life of the 

 plant, with the exception of the early juvenile 

 period. 



Eucalyptus Globulus, the Australian gum- 

 tree, has opposite and broadly sessile leaves 

 during the first years of its life. Later these 

 disappear and are replaced by long sickle- 

 shaped foliage organs, which seem to be scat- 

 tered irregularly along the branches. The juve- 

 nile characters manifestly lie dormant during 

 the adult period, and that this is so, may be 

 shown artificially by cutting off the whole crown 

 of the tree, when the stem responds by produc- 

 ing numerous new branches, which assume the 



