ALG^. 



91 



oogonia, because they enclose the ovum, or egg-like 

 body which is to become the fertilized oospore, and 

 reproduce the original plant. When the oospore 

 ultimately takes form it is globose, or elliptical, at 

 first of a green colour, but finally brown, and lies 

 freely within its mother-cell. This mother-cell, or 

 oogonium, in addition to its inflation, becomes 

 modified in another way, 

 since it splits all round, 

 above the middle, and 

 the upper part divides 

 from the lower, like the 

 lid of a box, leaving a 

 slit-like opening, through 

 which communication 

 from the exterior may 

 be made with the spheri- 

 cal body, or oospore, 

 nestling within (Fig. 14, b). 

 mon modification ; but in rarer instances, instead of 

 splitting all round and forming a lid, a perforation or 

 opening is made in the wall of the mother-cell for 

 external communication (Fig. 14, a). Hence it may 

 be said that some oogonia open with a lid, and some 

 are only perforated at the side by a pore. Whilst this 

 process of development is going on in the specialized 

 female cell, and it becomes changed into an inflated 

 mother-cell, or oogonium, enclosing the incipient 

 oospore, or ovum, other cells are undergoing change 

 upon the same thread, in order to become differentiated 

 into active male cells. These latter are much shorter 

 than ordinary cells, and may be single, or four to six 



Fig. 14. — Oogonia ; a, with lateral pore ; 

 b, with splitting operculum. 



This is the most com- 



