142 A TEXTBOOK OF THEORETICAL BOTANY 



chromosome number to one half. The eight nuclei separate and the cytoplasm 

 splits into eight portions, each with one nucleus. Each of these eight cells 

 is termed an oosphere. When they are mature the outer wall (exochiton) 

 of the oogonium breaks and the eight cells are liberated as a package contained 

 in an inner wall (mesochiton). In the sea water this inner wall also opens, 



Fig. 130. — Fiicus serratus. A, Mature oogonium containing eight oospheres. 

 B, Liberation of packet of oospheres from outer wall of oogonium. C, Libera- 

 tion of separate oospheres by solution of endochiton. {After Thuret.) 



and the innermost coat of mucilage (endochiton) disperses and the eight 

 oospheres escape as passive spherical bodies. Each oosphere contains many 

 plastids, giving it an olive-green colour. Interspersed with the oogonia 

 in the conceptacles are long sterile hairs, or paraphyses, which arise all over 

 the surface of the walls of the conceptacle, while their free ends project out 

 of, or at any rate towards, the pore or ostiole of the conceptacle. 



The male reproductive organs or antheridia arise in much the same way 

 as the oogonia from the surface of the male conceptacles. A superficial cell 

 grows into a short branched structure, with both sterile and fertile branches 

 (Fig. 131). The latter are the antheridia. The conceptacle is almost filled by 



Eyespot 

 Nucleus 



Fig. 131. — Fucus serratus. A, Antheridia on a branched filament. B, Ripe 

 antheridium. C, Detached antheridium D and E, Liberation of anthero- 

 zoids. F, Antherozoid. (After Thuret.) 



