152 THE FEUIT 



THE SEED 



333. Seeds are the final product of the flower, to which all its parts 

 and offices are subservient. Like the ovule from which it originates, 

 a seed consists of coats and kernel. 



334. The seed coats are commonly two, 

 the outer aud the inner. Fig. 275 shows the 

 two, in a seed cut through lengthwise. The 

 outer coat is often hard or crustaceous, whence 

 275. a, hilum; 6, testa; ^ i g called the testa, or shell of the seed; the 

 c, inner coat; d, inner is almost always thin and delicate, 

 albumen; e, em- 335. The shape and the mar ki llgs , so vari- 

 ous in different seeds, depend mostly on the 



outer coat. Sometimes this fits the kernel closely; sometimes it is 

 expanded into a wing, as in the Trumpet Creeper (Fig. 276, a), and 

 occasionally this wing is cut up into shreds or tufts, as in the .Catalpa 

 (Fig. 276, ft) ; or instead of a wing the seed may bear a coma, or tuft 

 of long and soft hairs, as in the Milkweed or Silk weed 

 (Fig. 276, c). The use of wings or downy tufts is to render 

 the seeds buoyant for dispersion by the winds. This is 

 clear, not only from their evident adaptation to this pur- 



276. Seeds fitted by outgrowths of the testa for dispersion by the winds : 

 a, Trumpet Creeper; 6, Catalpa; c, Milkweed. 



pose, but also from the fact that winged and tufted seeds are found 

 only in fruits that split open at maturity, never in those that remain 

 closed. The coat of some seeds is beset with long hairs or wool. 

 Cotton, one of the most important vegetable products, since it forms 

 the principal clothing of the larger part of the human race, consists 

 of the long and woolly hairs which thickly cover the whole surface 

 of the seed. There are also crests or other appendages of various 

 sorts on certain seeds. A few seeds have an additional, but 

 more or less incomplete, covering outside of the real seed 

 coats, called an 



336. Aril, or arillus. The loose and transparent bag 

 which incloses the seed of the White Water Lily (Fig. 277) 

 is of this kind. So is the mace of the Nutmeg. The aril is 

 a growth from the extremity of the seed stalk, or from the 

 placenta when there is no seed stalk. 



A short and thickish appendage or outgrowth around the micropyle 

 in certain seeds is called a CARUNCLE (Fig. 278). 



