238 



GENERAL BOTANY 



Conceptacle 



Both male and female gametangia arise from the cells bound- 

 ing the walls of the male and female reproductive cavities as 

 hairlike cellular outgrowths, not unlike a root hair growing from 

 an epidermal cell of a root tip. 



In the case of the female gametangia each initial hairlike game- 

 tangium cell divides to form one or more stalk cells and a ter- 

 minal cell, which enlarges to form the gametangium proper 



(Fig. 127). This female gametan- 

 gium in Fucus differs materially 

 from that of the green algse in 

 forming more than one gamete 

 in each gametangium. We shall 

 therefore expect to find the process 

 of gametogenesis much more com- 

 plex in Fucus than in Spirogyra, 

 where the entire protoplast of an 

 ordinary cell simply contracts and 

 rounds up to form one gamete. In 

 the male cavity each initial hair- 

 like cell divides into a cell chain 

 and branches repeatedly, forming 

 a shrublike system of branched 

 filaments. The end cells of these 

 branches develop the gametangia, 

 in which numerous male gametes 

 are formed during gametogenesis. 

 Cramete formation takes place by similar processes in both 

 male and female gametangia, although the gametes which result 

 are very different, both in number and in size, in the two cases. 

 Three essentially distinct processes are involved in this forma- 

 tion of the male and female gametes, namely, nuclear division, 

 cell division, and gamete differentiation (Fig. 128, a-c). 



Nuclear division takes place first in each gametangium, forming 

 eight free nuclei in the female gametangium and sixty-four in the 

 male gametangium. These nuclei soon become uniformly distrib- 

 uted throughout the cytoplasm of each large gametangium cell, 

 and then an internal process of cell division follows which results 



Paraphysis 



FIG. 127. Female receptacle and 

 conceptacles of Fucus 



a, female receptacle and ostia; b, 



transverse section of a, showing. con- 



ceptacles; c, enlarged conceptacle, 



oogonia, and paraphyses 



