330 REPRODUCTION IN PLANTS 



the same time absorbs supplies of water and dissolved 

 food from the original plant. The capsule at the top de- 

 velops a multitude of small wind-borne spores. The 

 stalk serves to lift the capsule up where the spores can be 

 advantageously scattered. It should be noted that while 

 this small attached plant is dependent on the first genera- 

 tion, it becomes green as soon as it is pushed out 

 of the enclosing structure and is exposed to light. It can, 

 therefore, manufacture a part at least of its carbohydrate 

 foods. 



Gametophyte and Sporophyte (Fig. 84). — In the 

 above account it is to be recognized that a green inde- 

 pendent moss plant produces the gametes (eggs and 

 sperms) and that the fertilized egg grows into a small 

 plant which in respect to water, salts, and part of its food 

 is parasitic on the first and which produces air-borne 

 spores which grow into the gametophyte or sexual genera- 

 tion. The first stage is called the gametophyte because 

 it produces gametes. Reproduction is brought about by 

 the regular alternation of these two generations. Every 

 alternation of generations in the higher plants involves 

 essentially this same cycle. 



Ferns show the same alternation of generations as do 

 mosses. There is, however, this striking difference, — the 

 fern plant familiar to everyone is the sporophyte 

 (Fig. 85) generation. The gametophyte (Fig. 86) gen- 

 eration is so small — a quarter of an inch or less in 

 diameter — that it is ordinarily overlooked except by 

 those who know about it and especially look for it. An- 

 other important difference is that, whereas the moss 

 sporophyte is small and attached (parasitically for all 

 its water and part of its food supply) to the green 

 gametophyte, the fern sporophyte is proportionately very 

 large, green, and therefore independent. 



The Structure of Ferns. — For present purposes it 

 is necessary to consider a few of the details of structure. 

 In the first place it is clear from the most casual observa- 



