142 



COMPENDIUM OF GENERAL BOTANY. 



essential part of plant -nutrition. Of the four important conditions 

 coming under this heading three are widely distributed and shall 

 receive our immediate attention. 



(a) Condition of Seeds before the Seginmng of Assimilation. 



The undeveloped embryo, which, when mature, becomes sepa- 

 rated from the mother-plant, receives a greater or lesser supply of 



stored food-substances during its 

 attachment to the mother-plant, 

 which serve as the initial food- 

 supply during germination. This 

 is very marked in our cereals. The 

 mass of the grain consists of stored 

 food-substance, the starch-bearing 

 endospermous tissue y 1 the small 

 embryo (see Fig. 82) is situated at 

 one side. We may obtain a better 

 summary of various seed- structures 

 by separating them as to their com- 

 position and mode of appropriating 

 or reabsorbing the stored food-sub- 



FIG. 82. Longitudinal median sec- stance. 



tion through the seed of Zea Mays. -, m i 



*, Epidermal layer ; n, point of attachment 1- 1* embryo 08868868 a Spe- 



of the style ; fs, base of the ovary eo -i n i 1*111 *i fee. J.T 



compact and ew less compact" portion of Cial flat shield-like Organ (" SCUtel- 



the endosperm ; sc and ss, scutellum (ab- , . , N , ,. .. .. . 



sorbing organ) with epider in is e ; fc, young mm ) WuOSe junction it IS to ab- 



leaves ; st, first iiiternode of the stem ; 



w, main root ; w', lateral roots springing S Qrb the f OOd-SllbstanCCS of the en- 



from the stem ; tvs, root-sheath. (After 



Sachs -) dosperm. This organ sometimes 



develops papillse-like projections, which penetrate the endosperm- 

 tissue in order to facilitate the absorption of the food-material 

 (grasses; see Fig. 82). 



2. Among certain palms there is a wart-like apical portion of 

 the cotyledon which serves to absorb the food-material. 



3. The cotyledons themselves are very frequently the bearers 

 of the reserve food- substance ; examples : Quercus-seeds, beans, 

 peas, lentils, etc. In the beginning the cotyledons are fleshy, sub- 

 sequently they shrink, as the food-material is removed during germi- 



sc 



1 Iu this case the expression " seed-albumen " is chemically incorrect, since the 

 substance consists essentially of a carbohydrate. 



