88 



BOTANY AND PHARMACOGNOSY. 



stitutes the gametophyte. It is thus seen that in the female 

 gametophyte of the Angiosperms archegonia are apparently not 

 formed. The gametophyte, then, consists 'of the cell group con- 

 taining the egg and the remaining portion of the embryo-sac, 

 which latter may be compared to a prothallus. This comparison 

 is not difficult to understand if we bear in mind the structure of 

 the gametophyte in the Gj'mnosperms and particularly if we recall 

 the structure in the higher Pteridophytes. 



Fig. 57. Development of embryo in the shepherd's purse {Capsella Bursa-pastoris), 

 I-VI, various stages of development; Vb, apex of the root seen from below, i, i, 2, 2, the 

 first divisions of the apical cell of the pro-embryo (suspensor); h, h, cells from which the 

 primary root and root-cap are derived; v, the pro-embryo; c, cotyledons; s, apex of the 

 axis; w, root. — After Hanstein. 



Fertilization.- — While in the gymnosperms the pollen 

 grains are usually provided with wings so as to bring about their 

 transferral to the carpel by the agency of the wind, in the angio- 

 sperms, on the other hand, the grains are not provided with wings, 

 but are adapted to transferral by insects. Pollination, however, 

 may be also effected by the wind as is the case with many of our 



