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- 

 carps are known as samaras or key fruits. 



Fig. 227. — Key of 

 Sugar Maple. 



Fig. 228. — Key 



of Common 

 American Elm. 



Maple (Fig. 



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



