152 



THE FUUIT 



THE SEED 



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

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

 a seed consists of coats and kernel. 



334. The seed coats are commonly two, 

 the outer and the inner. Fig. 27.5 shows tlie 

 two, in a seed cut through lengthwise. The 

 outer coat is often liard or cru.staceous, whence 



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

 inner is almost alwa3-s thin and delicate. 



335. The shape and the markings, 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, //) ; or instead of a wing the seed may bear a coma, or tuft 

 of long and soft hairs, as in the Milkweed or Silkweed 

 (Fig. 27G, e). The use of wings or downy tufts is to render „, 



the seeds buoyant for disper.sion by the winds. This is iitllJyifi 

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



a, hilum; h, testa; 

 c, inner coat; d, 

 albumen ; e, em- 

 bryo. 



270. Seeds fitted liy ontsvowlbs of (he testa for di.spersiou by the winds: 

 a, Truiuin't Creepur; h, Catulpa; e, Milkweed. 



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

 (inly iu fruits tliat split open at nniturity, never in those that remain 

 dosed. The cnat of some seeds is beset with long hairs or wool. 

 ('iiUnii. 01M-' of the most important vegetable products, since it forms 

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

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

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

 soi-ts on certain seeds. A few seeds have an additional, but 

 more or less inromplete, covering outside of the real seed 

 rnats. called an 



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

 whifh inelos(^s tlie seed of llie White Water Lily (Fig. 277) 

 is of this kind. So is the in'ice of the Xutmeg. The aril is 

 a growth fi-om thi^ extieiuity of the seed stalk, or from the 

 placenta when tliei'e is no seeil stalk. 



A short and tlnrki>li :i]-ipcu(lage or outgrowth around the micropyle 

 in certain seeds i- ca'.lt'd a C.^ru.n'Cle (Fig. 278). 



