112 GERMINATION OF THE MEGASPORE 



and note the character of the plant that develops from it. As 

 has been stated this spore is never discharged from the ovule 

 within which its entire growth occurs. The first indications of 

 germination are seen in the enlargement of the spore and the 

 division of its nucleus into two nuclei, which separate and move 

 to either end of the spore (Fig. 77, A). The food for the nourish- 

 ment of the growing megaspore is derived from the cells of the 

 nucellus which are dissolved and absorbed as the megaspore 

 increases in size, and food is also conducted to it from the parent 

 plant by means of the funiculus. Each of the two nuclei at the 

 end of the spore divides again, thus forming two nuclei at either 

 end. This process is repeated once more so that we now find four 

 nuclei at the ends of the spore which has become somewhat elon- 

 gated (Fig. 77, B, C). The so-called polar nuclei, a nucleus 

 from each end, now move toward the center of the spore and 

 fuse, forming one nucleus. This completes the germination of 

 the megaspore and we see that it has grown into a sac-like plant 

 consisting of seven cells, or nuclei imbedded in a mass of proto- 

 plasm (Fig. 78). The cells of this minute plant differ in char- 

 acter and perform very different duties. For example, the larger 

 cell toward the micropylar end of the plant is the female cell or 

 egg cell. It will be called the female gamete because it unites 

 with another cell, the male gamete. The two small cells near the 

 female gamete are the synergidae or cells that assist in the 

 nourishment and later development of the female gamete. The 

 two cells fusing in the center of the plant form the endosperm 

 nucleus which later by repeated divisions produces a mass of 

 nourishing cells that fill the space within the sac. The three 

 cells at the bottom of the sac, known as the antipodal cells, may 

 increase in number and take part in the later growth, but as a 

 rule they are disorganized and used for food. They are often 

 provided with cell walls, the other cells consisting only of a 

 nucleus and a varying amount of cytoplasm. This plant formed 

 by the germination and growth of the megaspore is called the 

 female gametophyte, because it contains the female gamete, and 

 you will see that a corresponding plant appears in the ferns and 

 other groups of plants. 



