278 A TEXTBOOK OF GENERAL BOTANY 
ovary composed of a single carpel. The follicle splits along 
one side only (Fig. 259), while the legume, which is the char- 
acteristic fruit of the pea or bean family, usually splits along 

Fig. 264. Longitudinal 
two edges (Fig. 260). 
Achenial fruits. An achene is a small, 
dry, indehiscent, one-seeded fruit (Fig. 
261). The achenes of the sunflower are 
sold under the name of sunflower seed. 
The caryopsis, or grain, differs from the 
achene in that the pericarp, or wall, of the 
fruit, is fused with the testa (the outer coy- 
ering of the seed). The grain is the typi- 
cal fruit of the grasses, and its structure can 
sectionofdrupeof peach. be observed very 
(X 2) clearly in corn (Fig. 
303). The samara 
is a winged achene (Fig. 262). The nut 
is a one-seeded, usually indehiscent fruit 
in which the wall of the fruit, or the 
pericarp, is hard. Many structures which 
are popularly called nuts do not fit this 
description. 
Schizocarpic fruits. These are dry fruits 
which split up into a number of one-seeded, 
usually indehiscent parts (Fig. 268), as in 
the castor-oil plant. 
Drupes. A drupe is a fruit in which the 
inner part of the pericarp (ripened ovary 
wall) is hard and the outer part fleshy or 
fibrous (Figs. 264, 265, 304). In the peri- 
carp of the drupe there are three regions : 

Fig. 265. Longitudinal 
section of drupe of mango 
(Mangifera indica). (x }) 
the epicarp, or outer 
skin ; the mesocarp, or middle fleshy or fibrous region; and the 
endocarp, or hard inner portion which forms the stone inclosing 
the seed. Many structures popularly known as nuts are com- 
posed of the endocarps and the seeds of drupes. The walnut 
and the almond are examples. 
