368 



PLANT STUDIES 



The female gametophyte develops within the embryo- 

 sac, and consists at first of seven independent cells, one 

 of which is the egg, no archegonium being formed. The 



Fig. 328. Development of embryo of shepherd's purse (Capsella), a Dicotyledon; 

 beginning with /, the youngest stage, and following the sequence to VI, the old- 

 est stage, V represents the suspensor, c the cotyledons, s the stem-tip, ^v the root, 

 h the root-cap. Note the root-tip at one end of the axis and the stem-tip at the 

 other between the cotyledons. — After Hanstein. 



egg is in the end of the sac nearest the micropyle, in the 

 most convenient position for the entering tnbe. AVhen the 

 tip of the pollen-tube enters the sac it discharges the two 

 male cells. One of these unites with the egg and forms 

 the oospore, which germinates and forms the embryo. The 

 other male cell unites with one of the other free cells of 

 the female gametophyte and forms the " endosperm cell," 



