THALLOPHYTA: FUNGI 



ni 



of these cells becomes a sporangium and, when conditions are favorable, 

 gives rise to a number of naked zoospores (usually 8 to 12) that escape. 

 Frequently, however, the resting cell arising from a vegetative protoplast 

 divides to form a number of gametangia rather than sporangia. Each 

 of these produces many isogametes that, after escaping, fuse in pairs. 

 The zygote invades a host cell and then goes into a resting stage, forming 

 a thick wall. Later it gives rise to many zoospores. Both the zoospores 

 and gametes of Synchytnum are uniciliate. 



Summary. Most of the Chytridiales are unicellular fungi with either 

 no mycelium or a ver}^ poorly developed one. Generally all or most of 

 the vegetative body develops into a sporangium or gametangium. 

 Reproduction occurs by uniciliate zoospores or isogametes. Because 

 they possess the simplest tj^pe of sexual reproduction known among the 

 fungi, the Chytridiales are regarded by some mycologists as primitive 

 forms, while others consider them to be degenerate Phycomycetes. 



2. Monoblepharidales 



The Monoblepharidales are a very small order containing 2 genera: 

 Monoblepharis, with 6 species, and Monoblepharella, with 2 species. 



ABC 



Fig. 87. Monoblepharis sphaerica. A, end of hypha with young oogonium and a young 

 antheridium just below it; B, sperms escaping and approaching the mature oogonium with 

 its single egg; C, zygote with empty antheridium below it. (After Cornu.) 



Monoblepharis is a saprophyte on decaying aquatic vegetation. It has 

 a well-developed mycelium that produces sporangia and sex organs. 

 The sporangia are terminal club-shaped cells containing many vmiciliate 

 zoospores. Sexual reproduction is heterogamous. The oogonium is a 

 globular cell, cut off by a wall commonly at the end of a hypha (Fig. 87). 

 Its protoplast rounds up and becomes a large uninucleate egg. The 

 antheridium usually arises immediately below the oogonium as a short 



