136 



DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



The above phenomena close the cycle of development and in some species the 

 course of development is actually limited to them ; many observations at least have 

 failed to detect anything further, for example in Pythium vexans and Artotrogus. 

 We may therefore conclude that the essential points in the life-history of the whole 

 group are confined to these phenomena. 



But in most species there is this difference, that the course of the development 

 is extended by the intercalation of numerous propagative cells, gonidia. In some 

 cases indeed the formation of gonidia is actually a necessary part of the entire 

 development; the germ-tube which proceeds from the oospore developes into 



FlG. 63. Cystopus Candidas. A mycelium with young oogonia og. B oogonium og with oosphere as and antheri- 

 dium an. C mature oogonium og, oospore os. D ripe oospore in optical longitudinal section. , f, G formation of 

 swarm-spores from oospores ; i endosporium. Magn. 400 times. 



a small rudimentary plant, which we may call a promycelium (see on page 

 in), and this produces 'a few gonidia and then dies, while the gonidia give 

 rise to new perfect fertile plants. This is the case with Phytophthora omnivora 

 and Pythium proliferum which represent the intermediate mode of germination 

 mentioned above. A very large majority of species, the two last-named among the 

 number, form gonidia, not or not only in the way just described as terminal 

 members of a short-lived alternate generation, but as accessory products of every 

 normally developed thallus ; the gonidia are usually produced in such large quan- 

 tities as to further the propagation of the species to an enormous extent by their 

 germination, and they have such characteristic forms, that the characters of species, 



