142 



COMPENDIUM OF GENERAL BOTANY. 



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

 coming under this heading tliree are widely distributed and shall 

 receive our immediate attention. 



(^a) Condition of Seeds he fore the Beginmng 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 

 endosjjennous tisstie ^ ' 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. 83.— Longitudinal median sec- stance, 

 tion through the seed of Zea Maiis. -i rri i 



c. Epidermal layer ; n, point of attachment 1- J-lie embryO pOSSCSSeS a SpC- 



of the style; /s. base of the ovary; eq •ijij.i-iiti /ll i. ^ 



compact and ew less compact portion of Ciai Iiat Shield-ilke Organ (" SCUtel- 

 the endosperm ; sc and .Si', scM^eZ/wm (ab- - i,n i i- ,• •. • . i 



sorbing organ) with epidermis e ;A;, young lum ) whOSC lUnctlOU it IS tO aO- 

 leaves ; st, first internode of the stem ; « 



w, main root ; w', lateral roots springing gorb the f OOd-SubstanCCS of the en- 

 rrom the stem ; ws, root-sheath. (After 



^^^^s) dosperm. This organ sometimes 



develops papillee-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- 



iJ^' 



' In this case the expression " seed-albumen " is chemically incorrect, since the 

 substance consists essentially of a carbohydrate. 



