62 THE GROWTH AND PARTS OF PLANTS 
those of the oak, elm, maple, apple, bean, pea, and 
maize, are broad and thin. ‘The grass leaves are long 
and narrow, but they are thin. If you have gathered 
some pine leaves, or leaves of the yew, cedar, fir, 
juniper, or larch, you see how very different they are 
from the other leaves. Perhaps you have never heard 
of leaves on the pine, for they are often called pine 
needles, because of their needle-like shape. They are 
not so thin as most other leaves, and they are stiff. 
Did you ever see the stonecrop, which grows in dry, 
sandy places? Its leaves are not very large, and they 
are thick. So we find that while most green leaves are 
broad and thin, some are not. You see how quickly 
the thin leaves wilt and dry after they are picked. But 
the stonecrop leaves do not wilt so easily. On hot days, 
durmg a long “spell of dry weather,’ did you ever 
notice how many of the plants with green leaves wilt 
and suffer for want of water? At such times how is it 
with the stonecrop ? 
Note. — During late summer and autumn the leaves of many trees 
take on bright colours, such as red, yellow, etc., of varying shades. The 
pupils interested in gathering leaves will be attracted by this brilliant 
foliage. The beautiful colouring is the expression of certain changes 
going on inside the leaf during its decline at the close of the season. 
The causes of thege colours form too difficult a subject for discussion 
here. But it should be understood that the « autumn colours ” of leaves. 
are not necessarily due to the action of frost, since many of the changes 
occur before the frosts come. | 
