STRUCTURE AND DEVELOPMENT. 55 



bouring antheridia adhere and through which they 

 penetrate to the oosphere within. Presumably the 

 process described by De Bary in the one species 

 (Chara vulgar is) prevails in the other Charophytes 

 in which the coronula is persistent. In species in 

 which it is deciduous the apices of the spiral-cells 

 dilate instead of lengthening, and when the coronula 

 falls a direct apical approach to the oosphere is 

 formed through which, there can be little doubt, 

 fertilization is effected. 



After fertilization the oosphere becomes an oospore 



FIG. 24. i. Fully developed oogonium of Chara vulgaris ( x60) (after 

 Migula). ii. Fully developed oogonium of Nitella tenuissima 

 ( x 140) (after De Bary). 



and other changes take place in the oogonium 

 (Pig. 24). 



If now the matured oogonium be ex- 



at ! lre amined in detail it will be found to 

 oogonium. . , G f 



consist in the first place ot an outer 



integument formed by the union of the outer walls 

 of the five enveloping cells. This integument can be 

 removed in one piece, laying bare the inner proto- 

 plasmic contents of the spiral-cells adhering to the 

 oospore. The protoplasmic contents still maintain 

 the form of coils and can be unwound and laid out 

 in separate strands. The posterior walls of the 



