THE NUT 



87 



(Fig. 64, a), but if it does not open until burst by the germi- 

 nating seed, it is indehiscent. (Fig. 64, b.) 



The term pod or capsule will apply to any of the dehiscent 

 fruits, regardless of the number of carpels involved in its 

 formation. The term legume applies to those peculiar elongated 

 pods (Fig. 64, a) of the leguminosece or pea family, each of 

 which represents a single capsule of two valves and a single 

 placenta. 



The indehiscent fruits are : 



(a) The achene, a small, dry, one-seeded pod representing 

 one or more carpels. (Fig. 64, b.) 



FIG. 64. a, legume or dehiscent pod; b, an achene or indehiscent pod cut so as to show the 

 enclosed seed; c, caryopsis or grain showing the pericarp or ovary, the integument or seed 

 coat, the aleurone cells and the starch area; d, samara or key fruit; e, acorn or nut type. 



(b) The caryopsis or grain in which the pod or ovary is 

 united to the seed. (Fig. 64, c.) 



(c) The samara or key in which the pod is developed into 

 a thin flat wing. (Fig. 64, d.) 



(d) The nut is a single seed in which the ovary is developed 

 into a hard, bone-like or horn-like covering. 



There are several types of nuts, such as the acorn (Fig. 64, e) 

 which is a cup formed of involucral leaves ; the hazelnut, chest- 

 nut, and beechnut, in which the nuts are enclosed in a pod also 

 formed of involucral leaves ; the hickory nut inclosed in a shuck, 

 probably composed partly of calyx and partly of involucral 

 leaves, which tend to split when dry. The walnut is of the same 

 type as the hickory nut, but does not tend to split; it is some- 



