2 2 GENERAL MORPHOLOGY. 



and consequently a tendency to the production of spores is de- 

 veloped when the mycelium is constrained to exert a certain 

 force in order to extract the water from the nutrient substratum. 

 According to C. Tanret (I. and II.), AspergiUus niger will not 

 produce conidia when obliged to develop, at 3o°-40°C.,inaRaulin's 

 nutrient solution containing 0.5 gram, or more, ammonium nitrate 

 per 100 c.c, or larger quantities of the sulphate or chloride of 

 this base; whereas the process is stimulated by the presence of 

 even as much as 2 grams of ammonium phosphate. Free acid, 

 up to 0.4 gram per 100 c.c, is liberated from the first-named 

 salts. At 20^-22° C, on the other hand, even as much as i gram 

 of ammonium nitrate merely retards, without preventing, fruc- 

 tification. Experiments in the same direction have been made 

 by W. ScHosTAKOWiTSCH (I.), especially with Deniatium j^ullii- 

 lans, as will be found in a later section relating to this organism. 

 (See also § 229 and § 233.) 



In some fungi the conidiophores, instead of remaining sepa- 

 rate, arrange themselves in parallel order, side by side, at an 

 early stage, and thus unite to a fascicle, to which the name 

 core'mium has been given. In a still higher stage of develop- 

 ment the conidiophores — compressed together like a palisade — 

 and the chains of conidia thereon, are enclosed in a cover ; 

 which latter is developed from the adjacent mycelium, may con- 

 sist of one or more layers, and is closed on all .sides when young, 

 but afterwards opens to allow the ripened spores to escape. 

 These forms are termed pycnides, an example of which is 

 afforded by the secidia of corn mildew, Puccinia yraminis, 

 which occurs in the form of red patches on barberry leaves, 

 and, together with a number of similar parasites, constitutes 

 the class of the Uredince or rust fungi. These latter, as well as 

 the adjacent class of Vstilaginece or smut fungi, do not come 

 within the province of the present work, but are treated 

 thoroughly in handbooks on plant diseases. Technical Mycology 

 is concerned solely with certain genera of the Zygomycetes and 

 Ascomycetes, the first named being dealt with in Chapters xliii.- 

 xlv., and the others in succeeding chapters. 



It was stated in § 220 that sporangia make their appearance 

 in two different principal stages of development, and that the 

 higher of the two differs from the other by greater precision as 

 regards the number, form, and dimensions of the endospores, 

 produced in the sporangium (or ascus). A similar distinction 

 may also be made in connection with the foimation of conidia. 

 Among the Enmycetes thei'e exists a well-defined group of 

 fungi, in most species of which the conidiophores exhibit con- 

 stancy in I'espect of their form and dimensions, as well as with 

 regard to the number and form of the conidia they prodiice. 

 This fact has been expressed by the bestowal of a particular 

 nomenclature, such conidiophores being termed hasidia, and the 



