THE LEAF 195 



terns. This will lead to intorosting questions in regard to irrigation and 

 manuring. Where plants are crowded, the growth of both roots and 

 leaves is complicated with so many other factors that it is best to select 

 for observations of this sort specimens growing in more or less isolated 

 situations. 



Notice the time of the expansion and shedding of the leaves of different 

 plants, and whether the early leafers, as a general thing, shed early or late ; 

 in other words, whether there seems to be any general time relation be- 

 tween the two acts of leaf expansion and leaf fall. 



(4) Under Section VIII, look for instances of modified leaves ; study 

 the nature of the different modifications you find, and try to understand 

 their meaning and object. Make a collection (a) of all the leaves you can 

 find modified to serve other than their normal purposes ; (6) of all the 

 organs of other kinds that have been modified to serve as leaves ; (c) of 

 all the modified parts of leaves — stipules and petioles — that you can 

 find. Keep the collections separate, labeling each specimen with the 

 name of the plant it belongs to, what part it is, what use it serves, 

 when and where found. These collections need not be made individu- 

 ally, but by the class as a whole and kept for the use of the school. 



Observe also (d) the differences between young and old leaves of the 

 same kind, and the leaves of young and old plants or parts of plants of the 

 same kind ; (e) resemblances between young leaves belonging to plants of 

 different species ; (/ ) between young leaves of one species and mature ones 

 of one or more different species. Make a collection of all the specimens you 

 can find illustrating the three points mentioned, referring each to its proper 

 head, and giving the name and relative age — old or young — of all speci- 

 mens collected. 



