THE LEAF 195 
tems. This will lead to interesting 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 ; (f) 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. 
