WATER-PLANTS 51 
II. Floating Leaves. 
1. The Cireular or Orbicular Type.— Leaves of this 
kind float on the surface of the water—e.g., water-lilies, 
frogbit (Hydrocharis Morsus-rane, Fig. 19), the floating 
leaves of the water-buttercup (Ranunculus aquatilis). 
In some cases the leaf has an upturned margin, which 
diminishes the risk of capsizing (the great Amazon water-- 
lily, Victorrza regia). The petioles of these leaves are 
Fic. 18.—Formation or Broop-Bup in Potamogeton crispus. (ABOUT 
Hair Natura SizE. AFTER KERNER.) 
To the left a bud still attached to plant, to the right the separate bud. 
usually elastic and very flexible, so that they can, by 
coiling or uncoiling, adjust themselves to variations in 
the depth of the water. 
2. The Long Floating Ribbon-Type.—This differs in 
no respect from that previously described, except that 
it is not submerged. It is found in Sparganium natans, 
and in the floating manna-grass (Glyceria flwitans). 
Heterophylly (Gr. heteros, different; phyllon, leaf).— 
Some plants exhibit two types of leaves, one float- 
ing and the other submerged, and the two appear 
together on the same plant. Thus the water-buttercup 
has finely- dissected submerged leaves, and broadly- 
