182 



PLxVNT STKUCTURES 



little drift at the bottom of each carpel, where the ovules 

 are found (Fig. 147, A, B). The flaring lips of the micro- 

 pyle roll inward and outward as they are dry or moist, and 

 by this motion some of the pollen-grains are caught and 

 pressed down upon the apex of the nucellus. 



In this position the pollen-tube develops, crowds its 

 way among the cells of the nucellus, reaches the wall of 

 the embryo-sac, and penetrating that, reaches the necks 

 of the archegonia (Fig. 149, p, t) ; crowding into them 

 (Fig. 151), the tip of the tube opens, the male cells are 



Mi 



-^^Siiif 





Fig. 152. Fertilization in spruce {Piceaw B is an egg. in the tip of which a pollen 

 tube {p) has entered and has discharged into the cytoplasm a male nucleus (sn). 

 which is to unite with the egg (female) nucleus (o?i); C, a later stage in which the 

 two nuclei are uniting.— After Schimper. 



discharged, one male cell fuses with the ^gg (Fig. 152), 

 and fertilization is accomplished, an oospore being formed 

 in the venter of the archegonium. 



It will be noticed that the cell which acts as a male 

 gamete is really the sperm mother cell, which does not 

 organize a sperm in the absence of a water connection. 

 This peculiar method of transferring the male cells by 

 means of a special tube developed by the antheridium is 



