364 



BOTANY 



enveloped by a cortical layer consisting of longitudinal rows of 

 cells which develop at the nodes from the basal cells of the lateral 

 axes. 



As a result of the fragmentation of its original nucleus, each inter- 

 nodal cell is provided with a number of nuclei which lie embedded 

 in an inner and actively moving layer of parietal protoplasm. 

 Numerous chloroplasts are found in the internodal cells. 



Asexual reproduction by means of swarm-spores or other spores 



Fio. 299. Chara fragilis. A, Median longitudinal section through a lateral axis r, and the sexual 

 organs which it bears (x 60); a, antheridium borne on the basal nodal celllna, by the stalk 

 cell p ; m, manubrium ; ob, an oogonium ; no, nodal cell ; po, the stalk-cell ; v, pivotal cell ; 

 c, (the crown B a lateral axis (bearing axes of the third order (x 6); a, antheridium; o, 

 oogonium. 



is unrepresented in the Characeae. Sexual reproduction, on the other 

 hand, is provided for by the production of egg-cells and spermatozoids. 

 The female organs are ovate. They are visible to the naked eye, 

 and, like the spherical red-coloured antheridia, are inserted on the 

 nodes of the lateral axes. With the exception of a few dioecious 

 species, the Characeae are monoecious. 



The oogonia (Fig. 299 ob) contain a large ovum, filled with starch grains and 

 oil-drops ; this is surrounded by spirally wound tubular cells forming the envelope. 

 These tubes terminate in the crown (c) between slits in which the spermatozoids 

 enter. The antheridia (Fig. 299 a) possess a wall formed of eight flat cells with 



