SEXUA L REPROD UCT10N. 



293 



Loss of sexuality. 



396. Among fungi. — Though descended from ancestors 

 possessing sexual organs, certain groups of plants have lost this 

 mode Ox" reproduction and rely wholly upon non-sexual 

 methods. Such are the higher 

 fungi. The lower forms only 

 have sexual organs. These fungi 

 show their- relation to algae by 

 retaining in part or wholly aqua- 

 tic habits. In Cysiopus, for ex- 

 ample, at a certain stage zo- 

 ospores are produced ; and these 

 are generally characteristic of 

 aquatic plants, though Cystopus 

 has become a parasite upon land 

 plants. Many aquatic fungi are 

 known, most of which grow 

 upon dead plants or animals 

 (espe< ially insects) which have 

 fallen into the water. Not only 

 do many of these lower forms 

 produce zoospores, but the form 

 of their sex-organs and mode 

 of union remind one immedi- 

 ately of similar structure and 

 action in common algae. Com- 

 pare, for example, the sex- organs 

 in Vaucheria (fig. 308) and those oi Achlya (fig. 336). 



Some fungi possess sex-organs which are functionless, 

 although the egg de\ elops as though it had been fertilized I fig. 

 336). But in most, all trace of sexual organs has disappeared, 

 though many produi e spore-bearing structures, the fructifica- 



Fig. 336. — A. Functionless 

 of a fungus (Achlya <■ 



with 'i eggs . 

 spermaries from branches ol same 

 liyplia form fertilizing tube which re- 

 mains closed. /•'. eggs which have 

 tini; spuii's w itliout ferti- 

 lization. M.i.unilu-il .■!•-•. iliam. — After 

 s.n hs. 



