- which some of the leaves are 
ry a . 
‘ / Ae . ‘et 
The External Form of Plants. re cf 
or fi/zform as in the submerged leaves of Ranunculus aquatilis — 
(Fig. 177, p. 100), fistulose as in Allium carinatum, inflated 
as in the onion, or even ete as in the case of the 
pitchers of /Vepenthes (Fig. 193), [and a few other genera, 
the bladders of U¢ricularza (Fig. 356), &c.| Occasionally — 
the lamina 1s perforated (Fig. 194). 3 
It is not uncommon to find on the same plant leaves of 
different forms (Fig. 177, p. 100; Fig. 195), when the plant ts 
said to be heterophyllous. 1 
This is especially the case 
with many water-plants, in 
submerged, while others rise 
above the water or float 
upon it, as in the arrow- 
head, Sagztarta sagittefo- 
Yee, and. . water ges Oe 
Ranunculus aguatilts. Ss 
leaves which grow from the. r 
lower part of the stem, or S 
radical leaves, are. fre- 
quently different in shape 
from the upper ones [or _ 
cauline leaves attached to oe 
the stem]. 
_ With reference to their — 
consistency, leaves are her- 
baceous [7.e. thin and flaccid ], 
succulent asin the lettuce, NY 
coriaceous or leathery as in in 
the box or holly, or fleshy 
as in Pinguicula. Fic. 195. — Heterophyllous leaves of shep- 
herd’s purse, Capsella bursa-pastoris. 
The leaf is usually of 
symmetrical shape on each side of the mid-rib ; but some- 
times wnsymmetrical or oblique (Fig. 156, p. osy, as in the 
_ lime or Begonia, one side being larger than the other. 
