THE FUNGI 



163 



in succession back of the apex of the hyphse, which thus shows a 

 definite apical growth. 



Reproduction. Spores of various kinds are produced, sometimes 

 borne directly upon the mycelium, but more commonly confined to 

 special structures, the spore-fruit or sporocarp, which may reach a 

 large size in the large fleshy Fungi. Sexual reproduction has been 

 demonstrated in a small number of the Eumycetes, but in most of them 

 no trace of any form of sexuality has been found, although it is quite 

 likely that it exists in a larger number than is at present supposed. 



Biology. Both parasitic and saprophytic forms are found among 

 the Eumycetes. Some forms, like the Rusts and Smuts, are ex- 

 tremely destructive parasites, others, like the Mushrooms, Puffballs, 

 etc., are saprophytes, usually living upon dead vegetable matter. In 

 these forms the mycelium is buried in the nutrient substratum, only 

 the large sporophores being visible above its surface. 



CLASS I. ASCOMYCETES 



The Ascomycetes, or Sac-fungi, include the major part of the Fungi 

 and exhibit great 



variety in structure 

 and size, as well 

 as in their habits. 

 While they may de- 

 velop several kinds 

 of spores, there are 

 always found the 

 ascospores, which 

 are formed by free- 

 cell formation 

 within special cells, 

 known as asci. In 

 the lowest types, the 

 Hemiascii, the num- 

 ber of ascospores in 

 the ascus is large, 

 but in much the 

 greater number it is 

 regularly eight. 



Ascospore-forma- 

 tion. The young 

 ascus (Fig. 127, A) 

 in typical Ascomy- 

 cetes contains two 

 nuclei lying in the 



E 



D 



G 



FIG. 127.'Pyronema confluens. Development of the 

 ascus. (After HARPER.) A, ascogenous hypha, with 

 young ascus at the summit, containing two nuclei. 

 B, older ascus, the nuclei fusing. C, ascus with single 

 nucleus derived from the fusion of the two primary 

 nuclei. D, nucleus of ascus, dividing. E-G, develop- 

 .ment of the ascospores. 



