26 GENERAL MORPHOLOGY. 



Among the Eumycetes, the oidia and gemmas are the most 

 frequent varieties of fruit ; but this cu-cumstance, coupled with 

 the simplicity and uniformity of their structure, renders these 

 characteristics almost entirely valueless as a basis of classifica- 

 tion for the fvmgi, since this classification is mainly founded on 

 differences in the occui-rence, mode of production, and develop- 

 ment of one or more of the other three reproductive organs 

 (endospores, conidia, zygospores), in the species to be differen- 

 tiated. Fungi wherein these organs have not yet been observed, 

 or wherein the latter appear in a form which does not permit 

 their inclusion in the existing system, are set apart in a special 

 class as " Fungi imperfecti," a term, however, expressing not 

 incompleteness in the fungi themselves, but only in our know- 

 ledge concerning them. A few of these species, e.g. the 

 so-called Saccharomyces ajjiculatus, certain Mycodermas, the 

 Moniiice, the Toruhe, kc, fall within the province of the present 

 work, and will be dealt with fully in the final Section. 



§ 224— The Germination of Spores. 

 Their Tenacity of Life. 



The spore is ripe when it has acquired the capacity of de- 

 veloping into a new individual of the species from which it 

 originated. The first stage of this development is termed ger- 

 mination, and, in the case of endospores and conidia, is a com- 

 paratively simple process. It has already been fully discussed 

 in § 218, and illustrated in Figs. 92 and 93. Deviations from 

 the main lines theie laid down, however, sometimes occur ; and 

 with one of these we shall later on become acquainted in the 

 case of Saccharoniyces Ludwigii. While previous separation 

 from the parent plant is unnecessary for the commencement of 

 germination in the conidia, the endospores must have been set 

 free therefrom by the decomposition or breaking down of the 

 wall of the sporangium or ascus. More will be said on this 

 point in § 235. Special experiments by P. Lesage (III.) have 

 placed beyond doubt that the development to mycelium of a 

 spore geiminating on a solid nutrient substratum proceeds the 

 more rapidly and luxuriantly the higher the water-vapour ten- 

 sion of the superincumbent air. 



The germination of the zygospores commences by the burst- 

 ing of the episporium, and the extrusion of the endosporium, in 

 one or more places, by the pressure of the swelling cell contents. 

 When the zygospore is submerged in a liquid, the development 

 is of a vegetative character, a mycelium being produced ; but 

 when, on the other hand, the spore is exposed to the air, it puts 

 forth (fructificatively) a fiuit-bearing stem, which then produces 

 spores in its turn. An example of both instances, in zygospores 



