ANGIOSPERM^E. 



423 



development in the apical portion of the embryo sac, there is 

 a corresponding one in the basal portion. The protoplasm 

 gathers about certain points, and gradually condenses so as 

 to form as many free and naked cells (Fig. 308). These 

 soon become covered with cell-walls, and they then multiply 

 rapidly by fission, until they 

 fill up the embryo sac with a 

 continuous tissue, the endo- 

 sperm. (Consult p. 41, and 

 Fig. 33, A and B.) 



533. The Development of 

 the Embryo. (Figs. 309 and 

 310). As stated above, one of 

 the firjst results of the fcrtili- ^""sachs. 

 zation of the germ-cell is the formation of a row of from 

 two to many cells, the suspensor or pro-embryo, the first or 

 proximal cell of which is attached to the Avail of the 

 embryo sac close to the micropyle of the ovule ; its distal, or 

 free end, always grows toward the interior of the ovule, and 



Fig. 308. Posterior part of the em- 

 bryo sac of Viola tricolor, e, its wall ; #. 



ca ^ ty of the gac; K, K, young endo 



sperm-cells which have formed in the 

 pr. Highly magnifled.- 



Fig. 309. Embryos of AlHuni cepa. /., very yonn? stage ; c, f>. cells of otiflpensor ; 

 a, the single cell constituting the embryo ; , an unfertilized germ-cell. //., an older 

 stage, the embryo row two-celled , es, the wall of the embryo sac. ///., a still later 

 stage. Much magnified. After Sachs. 



its last cell becomes transformed by successive fissions into a 

 several-celled surface (/.,Fig. 3jW) ; by a continuation of the 

 process a many-celled solid body is formed (77. , Fig. 31l) ; 

 partitions then arise in the cells parallel to the surface, and 

 the external layer of daughter-cells thus formed constitutes 

 the dermatogen or primary epidermis (777, 



Fig. ato), 



