CHAPTER IX 



SEEDS 



Seeds are very variable in structure, so much so, in fact, 

 that scarcely any two seeds have a similar structure. It is 

 necessary, therefore, when examining seeds, to compare the struc- 

 ture of the seed under examination with authentic plates or 

 with the section of a genuine seed. The layers of the seed 

 are the spermoderm, perisperm, endosperm, and embryo. In 

 some seeds the spermoderm forms the greater part of the seed; 

 in others the perisperm is greatest in amount; in still others 

 the cotyledons make up most of the seed, as in the mustards. 

 The cells fomiing these different layers differ in form, structure, 

 and number; therefore it is not difhcult to distinguish and to 

 differentiate between the different seeds when viewed as a sec- 

 tion or as a powder. Almond is studied because it has most of 

 the layers and cells found in seeds. 



SPERMODERM 



The spermoderm is the thin, brown, granular-appearing 

 skin of the almond. The layers of the spermoderm are the 

 epidermis, the hypoderm, the middle layers, and the inner 

 epidermis. 



The epidermis consists of radially elongated, thick-walled 

 stone cells which occur alone or in groups of two or more, but 

 seldom as a continuous layer. The upper or outer part of the 

 stone cells is non-porous, but the inner walls are strongly porous 

 (Plate 123, Fig. i). 



The hypoderm. The cells forming the hypoderm are com- 

 pressed, the wall structure is practically indistinguishable, and 

 the whole mass is reddish brown (Plate 123, Fig. 2). 



Occurring in this brown layer are several vascular bundles 

 (Plate 123, Fig. 3). 



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