CHAPTER V. THE THALLOPHTYA. 



299 



Fig. 497. — Small portion of 

 Chara stem, showing one node on 

 which are borne an oogonium, a, 

 and an antheridium, b. c is a 

 leaf, most of the other leaves 

 having been removed. Enlarged 

 about ten diameters. 



from the base and coiled spirally around it, and these are sur- 

 mounted by a crown, which in Chara consists of five and in 



Nitella of ten smaller cells, which 

 originate from the others by transverse 

 division. Thus, just before maturity, 

 the germ-cell is completely enclosed, 

 but when ready for fertilization, an open- 

 ing occurs between the cells at the apex, 

 and this becomes filled with mucilage, 

 and the wall of the germ-cell is also 

 converted into mucilage at its apex, 

 permitting the entrance of the anthero- 

 zoids. The oogonium, when mature, is 

 oblong or ellipsoidal in form and of a 

 deep orange color. See Fig. 497. 



The antheridium is a spherical body 

 nearly as large as the oogonium, and 

 also orange -colored when ripe. Its 

 walls are composed of eight triangular 

 cells, whose edges are serrated or wavy, and nicely dovetail into 

 each other. To the centre of each one of these cells, and pro- 

 jecting interiorly, is at- 

 tached a cylindrical 

 cell, called the manu- 

 brium, and this bears 

 at its inner apex a 

 rounded cell called the 

 head-cell. This, in turn, 

 is surmounted by about 

 six smaller cells, from 

 which proceed a num- 

 ber of small, coiled fil- 

 aments, each made up 

 of about two hundred 

 disc-shaped cells. In 

 all, each antheridium contains from one hundred to two hundred 

 of these filaments. See Fig. 498. When the antheridium is ripe 

 the segments of the wall separate, and from each cell of the fila- 

 ments there escapes a minute, slender, coiled antherozoid, pro- 



-/ 



Fig. 498. — Segment of Antheridium of Chara. a, one 

 of the wall-cells ; m, manubrium; /, /, antheridial fila- 

 ments. Magnified about 100 diameters. 



