THALLOPHYTA— FUNGI 



81 



forms as Cystopus, where it at once gives rise to zoospores ; in 

 Pythium, &c., the promycelium is the sporophyte. Some forms 

 have apparently no such alternation, as the oospores give rise to 

 sexual plants. 



Sub-Class lY. — Ascomycetes. 



In this group the. mycelium is made up of a number of 

 ccenocytes, each of the apparent cells into which the hyphte are 



Fig. 833. 



Fig. 834. 



AV/. 83.3. Oogouia and antberidia of AcMva lignicoUi. The letters A to e 

 indicate the course of development. The protoplasm of a cell or branch 

 of a cell collects into a globular form A, b, and by the formation of a 

 septum, D q, becomes an independent cell (the oogonium). The proto- 

 plasm then breaks up into two or more parts, D, e, e (oospheres), which 

 quickly become spherical, as seen in D, secrete a cell-wall E, and become 



oospores. After Sachs. /'/gf. 834. Two gonidangia of Aclilya. a. Closed. 



B. Euptured and allowing the zoogonidia, a, to escape, h. Mother-cells of 

 the latter after escape of e, the zoogonidia, from them. 



di\dded containmg several nuclei. The mycelium is thus in- 

 completely septate. The fmigi are both saprophytic and para- 

 sitic. Sexual reproduction is said to occur in some forms, but 

 it is not undisputed. In many cases complex organs occur 

 which suggest sexuality, but it may be that, as in the Sapro- 



VOL. II. G 



