THB SEED. 



117 



CHAPTEK XIY, 



THE SEED. 



582. The seed is till perfected ovule, having an embryo formed with- 

 in, which is the rudiment of a new plant similar in all respects to the 

 original. The seed consists of a nucleus or kernel invested with 



583. The integuments or coverings. The outer covering is the 

 testa, the inner the tegmen, as in the ovule. The latter is thin and 

 delicate, often indistinguishable from the testa. 



463 



Seed of "Water-Lily (Nymphsea), enlarged section ; alb., albumen ; o, the embryo contained 

 in the embryo-sac ; s, secundine or tegmen ; p, primine or testa ; r, raphe, ar, aril; m, mi- 

 cropyle ; /, funiculus. 463, Seed of Beau. 464, Same, one cotyledon with the leafy embryo. 

 461, Seed of Apple. 462, One cotyledon showing the raphe and embryo. 4G0, Fruit of Mirabi • 

 lis ; embryo coiled into a ring. 454, Onion ; embryo coiled. 455, Convolvulus ; leafy embryo 

 folded. 456, Embryo of Cuscuta. 45T, Typha. 45S, Eanunculus. 459, Hop. 



584. The testa is either membranous (papery), coriaceous (leath- 

 ery), crustaceous (horny), bony, woody, or fleshy. Its surface is gen- 

 erally smooth, etc. (118, a). 



585. The coma must not be confounded with the pappus, which is a modi- 

 fication of the calyx, appended to the pericarp, and not to the seed, as in the aohe- 

 nia of the thistle, dandelion, and other Compositse. Ita intention in the economy 

 of the plant cannot be mistaken, serving like the pappus to secure the dispersion of 

 the seed, while incidently as it were, in the case of the cotton-seed, it furnishes 

 clothing and employment to a large portion of the human race. 



586. The aril is an occasional appendage, partially or wholly in- 

 vesting the seed. It originates after fertilization, at or near the hilum, 

 where the seed is attached to its stalk (funiculus). Fine examples are 

 seen in the gashed covering of the nutmeg, called mace, and in the scar- 

 let coat of the seed of staif-tree. In the seed of Polygala, etc., it is but 

 a small scale, entire or 2 -cleft, called caruncle. 



