FRUITS AND SEEDS 



187 



seed, there is no reason for the pericarp to dehisce. The 

 whole fruit is distributed as a single seed, and germinates 

 as a seed. For this reason many achenes are popularly 

 called seeds e.g., sunflower, buttercup, straw- 

 berry-pips, corn-grains, etc. 



A nut is a dry indehiscent several-seeded 

 fruit, which becomes one-seeded by abor- 

 tion. The hazel-nut is derived from a two- 

 chambered ovary formed of two carpels con- 

 taining several ovules. In some cases nuts 

 are enclosed in false envelopes developed 

 from bracts e.g., the acorn lies in a cupule, 

 or cup, formed of a multitude of coalescent 

 bracts (Fig. 84) ; the hazel is partially en- 

 closed in a membranous cupule ; beech-nuts 

 (mast) and edible chestnuts are enclosed, 

 three together, in a spiny fleshy shell 

 (Fig. 85). 



2. Capsular Fruits. These are dry, many- 

 seeded fruits which split open to allow the seeds to 

 escape. The dehiscence may take place in various ways : 



(a) By pores -e.g., poppies, snapdragon (Fig. 86). 



FIG. 83. 



SAMARA 

 or ASH. 



--a 



FIG. 84. NUT ( ACORN) 

 OF OAK-TREE. 



a, cupule. 



FIG. 85. FRUIT OF EDIBLE CHEST- 

 NUT. 



a, nuts ; b, cupule. 



(b) By teeth, into which the top of the capsule 

 separates -e.g., Lychnis, Silene (Fig. 87). 



(c) By lids e.g., henbane, pimpernel (Fig. 88), plan- 

 tain. 



(d) By longitudinal splitting e.g., willowherb, violet, 

 bluebell, wallflower, Iris (Fig. 89). 



