6lO LECTURE XXII. 



In such forms as Coleochaete, Vaucheria, Oedogonium, 

 Volvox, Sphaeroplea, and the Characeae, the distinction of sex 

 attains its fullest expression, in that the oosphere has lost 

 every trace of its primitive planogamete character. In these 

 Algae it is not extruded from the oogonium, but is fertilised 

 there by an antherozoid which makes its way into the organ. 

 In Vaucheria and Oedogonium the oosphere presents, like the 

 large planogamete of Cutleria, a well-defined receptive spot at 

 which the entrance of the antherozoid into the oosphere takes 

 place. 



Fig. 67 (after Pringsheim). Reproduction of Oedogonium. A zoospore. 

 B fertilisation. og oogonium. os oosphere. an antheridium (dwarf-male). 

 ad antherozoid entering s the receptive spot of the oosphere. 



This state of things, which is in fact the most perfect 

 manifestation of sex which is attained among plants, obtains 

 throughout the Mosses (Muscineae) and the Vascular Crypto- 

 gams (Pteridophyta). In all these plants there is a female 

 organ, the archegonium, in which, as in the oogonium of the 

 Algae, the female cell, the oosphere, is developed : the arche- 

 gonium differs from the oogonium in this respect only, that 

 whereas the former is usually multicellular, the latter is usually 

 unicellular. The male cells in these plants are antherozoids, 

 and the organ in which they are developed is termed an 

 antheridium. The antheridium of these higher plants differs 

 from that of the Algae in that it is multicellular, whereas in 

 the Algae it is commonly unicellular, though to this there are 

 exceptions, notably the Characeae, in which group the antheri- 

 dium is multicellular and of highly complex structure. In 



