ALBUMINOUS AND EX ALBUMINOUS SEEDS. 



181 



508. The so-called ''grains" of the cereals are fruits instead of 

 seeds ; the accompanying figures exhibit, therefore, not only the 



a b . d 



structure of the integuments of the seeds, but also of the ripened 

 ovarian wall. 



509. As shown in the " Structural Botany," page 309, the 

 nucleus of the seed consists of the embryo and its supply of 

 a b c food. If the store of food is wholly 



within the tissues of the embryo, the 



seed is said to be exalbuminous ; if partly outside of the embryo, 

 as, for instance, in the cereals here figured, it is said to be 

 albuminous. The albumen is the supply of food in the nucleus 

 of the seed which is not stored in the embryo itself. 



FIG. 138. Cross-section from the periphery of the fruit of Zea Mais, highly magni- 

 fied: a, fruit-capsule; b, seed-coat; c, adherent cellular layer; d, starch containing 

 albumen of seed. (Berg and Schmidt.) 



FIG. 139. A cross-section from the periphery of the fruit of Avena sativa, highly 

 magnified : a, chaff; b, fruit-capsule with the seed-coat ; c. a-lherent cellular layer ; 

 d. starch containing albuminoid parenchyma. (Berg and Schmidt. ) 



FIG. 140. Cross-section from the periphery of the fruit of Oryza sativa, highly mag- 

 nified: a, chaff'; It, fruit -capsule with seed-coat; c, adherent cellular layer; d, starch 

 containing albuminoid parenchyma. (Berg and Schmidt.) 



FIG. 141. Cross-section from the periphery of the fruit of Hordeum vuleare, highly 

 magnified: a, chaff'; b, fruit-capsule with the seed-coat; c, adherent cellular layer; 

 d, starch containing albuminoid parenchyma. (Berg and Schmidt. ) 



