CHARADES. 



67 



The female organ of reproduction (Fig. 61 -Z?, 63) is a small 

 modified shoot, whose apical cell functions as an oogonium, its 

 protoplasm forming the oosphere, which has a colourless receptive- 

 spot at the summit (Fig. 63 ). The oogonium is situated on a 

 nodal cell, from which 5 cells grow out in a circle and coil round 

 the oogonium, covering it with a close investment. These cells 

 divide once or twice at the top, so that 5 or 10 small cells are 

 cut off, which project above the oogo- 

 nium and form the so-called " crown " 

 (Fig. 63 fc). The crown either drops off 

 at fertilisation, or its cells separate to 

 form a central canal for the passage of 

 the spermatozoids. The wall of the 

 oosphere l above the receptive spot be- 

 comes mucilaginous, and allows the 

 spermatozoid to fuse with the oosphere. 

 The oospore, on germination (Fig. 64 sp), 

 becomes a small filamentous plant of 

 limited growth (Fig. 64 /, d, q, pi) the 

 proembryo and from this, as a lateral 

 outgrowth, the sexual generation is pro- 

 duced. 



The order is divided into two sub- 

 orders : 



A. NITELLEJ;. The crown consists of 

 10 cells ; cortex absent : Nitella, Toly- 

 pella. 



B. CHARES. The crown consists of 5 

 cells ; cortex present : Tolypellopsis, Lam- 

 prothamnus, Lychnotliamnus, Char a. 



Chara crinita is parthenogenetic ; in 

 large districts of Europe only female 

 plants are found, yet oospheres are 

 formed capable of germination. 



About 40 species of fossilized Chara, 

 determined by their carpogonia, are 

 known in the geological formations from 

 the Trias up to the present day. 



FIG. 64. Chara fragilis. Ger- 

 minating oospore (sp); i, d, g, pi, 

 form together the proembryo 

 rbizoids (w") are formed at d ; 

 w' the so-called tap-root; at g 

 are the first leaves of the sexual 

 plant, which appears as a lateral 

 bud. 



1 Before fertilisation the cosphere divides and cuts off at the base one or 

 more cells (polar bodies?), termed " wendungszellen." 



