14 



RE PR OD UCTION 



mation (internal cell division). In one of the great classes of 

 the fungi the spores are produced in membranous sacs called 

 asci {PL I, f. if) ; in the common mushroom and aUied fungi 

 the spores are borne on spicules {sterigmatd) which rise from 

 large cells known as basidia {PI. i, f. iS, ig). In various groups 

 of fungi reproductive bodies* ^re produced in a variety of ways, 

 some of the more common being as follows : 



1 . Sexual forms of reproduction. 



a. By the union of similar elements (conjugation) resulting in 

 the formation of a zygospore (black mould, PL 2, f. 4, 7, g). 



b. By the union of dissimilar elements resulting in the for- 

 mation of an oospore (downy mildew, PL J, f. 5). 



c. By the union of dissimilar elements which, followed by the 

 growth of an alternate stage (known as a sporophyte) results in 

 the formation of a sporocarp (pow^dery mildew, P/. 4, f. j). 



2. Asexual forms of reproduction. 



a. The formation of ciliated swarm spores within the cell by 

 the ordinary process of internal cell division. 



b. The formation of solitary conidia on simple or branching 

 hyphae (downy mildew, PL 3, f. 4). 



c. The formation of conidia in chain's by the successive 

 cutting oft' of the ends of certain hyphae (green mould, powdery 

 mildew, PL 4, f. 2, 4). 



d. The formation of sporangia or membranous receptacles 

 containing large numbers of spores (black mould, PL 2,f. 2, 8.) 



e. The formation of pycnidia or special receptacles of more 

 or less elaborate structure, from the walls of which the conidia are 

 produced (many leaf spot fungi, P/. j, f. 2). 



The end of a hypha which bears conidia is known as a conidio- 

 phore ; it may be merely of the same thickness as the hypha itself 



*Iii Sylloge Fungorum, Saccardo uses different terms for reproductive 

 bodies according to their method of formation and the group in which they 

 occur, e. ^. , sporae in the Hymenomycetes and Gastromycetes ; sporidia in 

 the Pyrenomycetes and Discomycetes ; sporidae in the Sphaeropsideae ; and 

 conidia in the Melanconieae and Hyphomycetes. For the present we shall 

 use only spores and conidia for these reproductive bodies. It must be 

 remembered that while their function is practically the same, they cannot 

 be regarded as homologous organs since their origin and method of for- 

 mation is often widely different. 



