THE FERN BULLETIN 



5 



cies. but since it is desirable that these variations from 

 the normal have a name to distinguish them, we may- 

 adopt for this one the name of pubescens which Mr. 

 Terry has suggested in correspondence regarding it. 

 —Ed.l 



BUT HALF A FERN. 



By YVillard X. Clute. 



Twice in the life-cycle of the ferns, each plant is 

 reduced to a single cell. The best-known of these re- 

 ductions is that in which the spores are produced on 

 the backs of the fronds, the other occurs on the pro- 

 thallium at the time when the new fern plant arises. 

 It is this second cell that really produces the fern plant, 

 although it is commonly believed that the spores found 

 on the backs of the fronds are the ones that do so. 

 These latter spores, called asexual spores because they 

 are not connected in any way with sexual processes, 

 are formed by the interior division of a cell and merely 

 produce the prothallium. It is only in exceptional 

 cases, to be mentioned later, that a new fern-plant 

 originates without the prothallium first forming a 

 special sexual cell or spore. In fact, the two kinds of 

 spores divide the life of the fern into two distinct 

 generations which alternate with each other, a pro- 

 thallium being first formed by the asexual spore and 

 this being followed by the production of a new fern 

 plant by a sexual cell in the prothallium. The sexual 

 cell is formed by the union of two other cells, usually 

 called gametes and the prothallium is therefore often 

 known as the gametophyte, while the fern plant pro- 

 ducing the asexual spores is called the sporophyte. The 

 fact that all the fernworts consist of two distinct gen- 



