STRUCTURE OF THE PLANT 



13 



others of five, and lastly of seven or nine leaflets; i.e. here 

 commence leaves like those of which the foliage of a 

 grown-up tree is generally composed. This passage 

 from the cotyledon to the true leaf has happened 

 gradually ; it includes a whole series of intermediate 

 forms. We receive involuntarily from the series the im- 



FlG. 2. 



Fig. 3. 



pression that one of these organs is formed from the 

 other, and that these are the intermediate stages 

 through which a leaf has to pass. 



Let us now consider the bud of a tree, say of a maple, 

 of a horse-chestnut, or of any bush, like that of the 

 currant. We find peculiar organs on the outside of 

 them : dark brown, thin, tough, sometimes sticky and 

 resinous scales. If we pull the bud to pieces or let it 

 open by itself, then tear off its parts one by one and 

 spread them out in a row, we notice the following facts. 



