408 



THE NON-VASCULAR PLANTS 



In ferns you will find that the sporophyte ceases to have 

 any nutritive connection with the gametophyte except when 

 it is very young. It becomes an independent plant which 

 makes its own food. It is the leafy part of the fern, while 

 the gametophyte is an insignificant 

 little structure which is rarely noticed. 

 Finally, in seed plants, we find that 

 sporophytes are the plants themselves, 

 while the gametophytes, which began 

 by being hosts of the parasitic sporo- 

 phytes, end in seed plants by being 

 themselves parasites, and the sporo- 

 phytes are their hosts. You have 

 already learned something of this in 

 studying the flower. (See page 268.) 

 Since a gradual increase of the 

 sporophyte and a corresponding de- 

 crease of the gametophyte is a univer- 

 sal characteristic of the plant kingdom, 

 we should naturally expect to find 

 that there is some advantage to plants 

 in this matter. This advantage is 



FIG. 204. An antheridium no t difficult to perceive. The thing 

 of moss discharging its , . , 

 contents. At the left a whlch makes the Sporophyte increase 



single sperm is shown, and become independent is that the 



Note that it has two cilia. nutritive WQrk of ^ plantj at first 



done by the gametophyte, is gradually transferred to the 

 sporophyte, while the thing which makes the gametophyte 

 decrease in importance is that it loses this nutritive work. 

 As you have noted, the sporophyte of lower plants gets its 

 food from the gametophyte, while in the higher plants 

 gametophytes get their food from sporophytes. 



