104 BOTANY 



not correspond with the large seaweed, but with a parti- 

 cular reproductive structure to which the latter gave rise. 

 The fern plant differs a good deal from the seed-bear- 

 ing plants which we have examined in the earlier 

 chapters. It has- as a rule only underground stems 

 which are known as rhizomes; each bears very few 

 leaves at or near its apex. The stem grows horizontally 

 under the surface of the ground, reacting to gravitation 



FIG. 41. Prothallus of fern. X5- 



in a way unlike either stem or root of the flower- 

 ing plant. The leaves emerge from the soil generally 

 rolled up in the form of a shepherd's crook, in conse- 

 quence of the great growth of the under surface. They 

 soon straighten themselves as the growth of the upper 

 surface becomes vigorous, just as in the case of the leaf 

 in the bud of the flowering plant. They are then found 

 to be very much divided, except in a few cases. Roots 

 are given off from the rhizome in large numbers. 



The structure of the fern rhizome differs in detail 

 from that of either type of flowering plant we have 



