OF LEAVES. 17 
exactly alike. Sometimes the same plant maintains leaves having 
less resemblance to each other than those of two different species. 
The Paper Mulberry (Broussoneti#), Fig. 94, has at the same time 
heart-shaped and lobed leaves. In the garden Valerian the lower 
leaves are entire, and those at the summit are deeply notched. In 
the Ranunculus aquatilis, Fig. 95, the leaves, which vegetate in the 
Fig. 94.—Branch of the Paper Mulberry (Broussonetia papyrifera)y 
water, are divided into thread-like expansions, so narrow that they 
Seem to be leaves reduced to their nervures, or skeleton, while 
those leaves which grow in the air are entire, and disk-like in 
form, and more or less notched. "When the common Arrow-head 
(Sagitaria) grows in brooks, its submerged leaves form long 
nibbons ; when they grow on the banks of great ponds or tanks, the 
emerged leaves resemble those of the Arrow-heads, Fig. 86. 
