SPXTION 15.] 



EMBRYO. 



3SG. The Kernel, or Nucleus, is the 

 coats. In many seeds the ker- 

 nel is all Embryo ; in otticrs 

 a large part of it is tlie Al- 

 bumen. For example, in Fig. 

 423, it is wholly embryo ; in 

 Fig. 422, all but the small 

 speck (^) is albumen. 



3S7. The Albumen or Endosperm of the seed is suiSciently charac- 

 terized and its office explained in Sect. III., 31-35. 



38S. The Embryo or Germ, wliicb is the rudimenttiry plantlet and the 

 final result of blossoming, and its development in genniuation have been 

 extensively illustrated in Sections II. and III. Its essential parts are the 

 Radicle and the Coli/ledomt. 



389. Its Radicle or Caulicle (the former is tiie term long and gener- 

 ally used in botanical descriptions, but the latter is tlie more correct cue, 

 for it is the inirial stem, which merely gives origin to the root), as to its 

 position in the seed, always points to and lies near the mieropyle. In re- 

 lation to the pericarp it is » 



Superior, when it points to the apex of the fruit or cell, and 

 Inferior, when it points to its base, or downward. 



390. The Cotyledons have already been illustrated as re- 

 spects their number, — giving the injportant distinction of Dicoty- 

 ledonous, Polycotyledonous and Monocotyledonous embryos (36-43), 

 — also as regards tlieir tiiickuess, v]\\ti\\Qx foliaceous ox fleshy ; 

 and some of the very various shapes and adaptations to the seed have been 

 figured. They may be straight, or folded, or rolled up. In the latter 

 case the cotyledons may be rolled up as it were from one margin, as 



in Calycanthus (Fig. 424), or from apex to base in 

 a ilat spiral, or they may be both folded {plicate) 

 and rolled up {convolute), as in Sugar Maple (Fig. 

 11.) In one very natural family, the Crucifersc, two 

 diU'ercut modes prevail in the way the two cotyledons 

 are brought round against the radicle. In one series 

 they are 



Fig. 420. Seed of a Violet (anatropous) : a, hiluin; b, rhaphe; c, chalaza. 



Fig. 421. Seed of a Larkspur (also anatropous); the parts lettered as in the last. 



Fig. 422. Tliesame, cut through lengthwise: a, the hilum; c, chalaza; d, outer 

 seed-coat; e, inner seed-coat; /, the albumen ; g, the minute embryo. 



Fio. 423. Seed of a St. John's- wort, divided lengthwise; here the whole kernel 

 is embryo. 



Fig. 424. Embryo of Calycanthus; ujiper part cut away, to show the convolute 

 cotyledons. 



Fig. 425. Seed of Bitter Cress, Barbarea, cut across to show the accumbent 



cotyledons. 426. Embryo of same, whole. 



