FILICINEM. 



473 



a simple cell ; a smaller or larger number of divisions usually takes place in its 

 lower part (Fig. 332, A — D). The embryo itself originates from the lower (epibasal) 

 half of the oospore. By the elongation of the suspensor and the compression and 

 absorption of the surrounding cells, the embryo is forced into the endosperm, in 

 which it now undergoes further development, as in Phanerogams. In the mother- 

 cell of the embryo (epibasal cell) two segments^ are in the meantime formed by 

 the wall II (transverse wall); out of each proceeds an embryo-leaf (cotyledon), 

 and a longitudinal half of the hypocotyledonary segment of the stem. The foot and 

 root originate besides from the right segment, and in the left (in the figure) segment 

 is formed the two-sided apical cell of the stem (Fig. 332, A, B). While the two 

 segments are becoming transformed by a number of cell-divisions into masses of 

 cells, of which an inner mass very soon separates itself as the procambium of the 

 axial bundle and a peripheral mass as dermatogen and periblem, a swelling is 

 produced laterally beneath the first leaf, forming the foot 2; by its increase the 



Fig. 332.— Development of the embryo of Selazinella Martensu (after Pfeffer) \ A, H lower part of the suspensor with 

 the first much-divided sejjments of the embryo, and the apical cell s of the future stem ; bb the first leaves ; C apical view of 

 the same ; D the apex seen from above in the act of forming two new apical cells, right and left ; /, //, /// the primary 

 walls of the primary apical cell ; /'— K//' the longitudinal walls by which the two new apical cells are formed. (/ basal 

 wall ; // transverse wall.) 



Stem is forced over to the other side (that of the younger segment); so that the 

 apex comes to lie horizontally, and afterwards is even directed upwards (Fig. 331 /); 

 and finally the bud, with its first leaves, the cotyledons, grows out upright from 

 the apical part of the macrospore when the embryo begins to increase in length. 

 The first root is formed a considerable time afterwards between the foot and 

 the suspensor. It is lateral, and its apical cell is formed from an inner cell of 

 the right segment; but the first layer of its root-cap originates from the splitting 

 into two layers of the overlying dermatogen ; the later layers of the root-cap arise 

 from the apical cell of the root itself. 



It has already been mentioned that in Pteris and Salvinia the position of the 

 apical cell of the growing stem is placed at an angle of about 90° with respect to 



^ [There is reason to believe that four octants are formed from the epibasal cell as in the other 

 "Vascular Cryptogams,] 



^ [On the propriety of regarding this organ as the morphological equivalent of the foot of the 

 other Vascular Cryptogams, see Quart, Journ. Micr. Sci. 1878.] 



