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 the leaves of the adult plant are lacking, 

 being 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 Ulex 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 disap- 

 pear and are replaced by long sickle-shaped 

 foliage organs, which seem to be scattered ir- 

 regularly along the branches. The juvenile 

 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 producing 

 numerous new branches, which assume the 



