1 64 



PLANT BIOLOGY 



fruit, as possibly in the walnut and hickory (Fig. 225), and 

 cup of the acorn (Fig. 226). The chestnut and the beech 

 bear a prickly involucre, but the nuts, 



FIG. 225. HICKORY-NUT. 

 The nut is the fruit, con- 

 tained in a husk. 



FIG. 226. LIVE-OAK ACORN. 

 The fruit is the " seed " part ; 

 the involucre is the " cup." 



or true fruits, are not grown fast to it, and the involucre 

 can scarcely be called a part of the fruit. A ripened ovary 

 is a pericarp. A pericarp to which other parts adhere has 

 been called an accessory or reenforced fruit. (Page 169.) 

 Some fruits are dehiscent, or split open at maturity and 

 liberate the seeds ; others are indehiscent, or do not open. 

 A dehiscent pericarp is called a / pod. 

 The parts into which such 

 a pod breaks or splits are 

 known as valves. In inde- 

 hiscent fruits the seed is 

 liberated by the decay of 

 the envelope, or by the 

 rupturing of the envelope 

 by the germinating seed. 

 Indehiscent winged peri- AMERICAN ELM. 

 carps are known as samaras or key fruits. Maple (Fig. 

 227), elm (Fig. 228), and ash (Fig. 93) are examples. 



FIG. 227. KEY OF 

 SUGAR MAPLE. 



FIG. 228. KEY 

 OF COMMON 



