70 



MANUAL OF BOTANY 



Fig. 820. 



M"^y5^- 



sexual apparatus is formed, but it is doubtful how far actual 

 fusion of the gametes takes place. 



The gametes may be alike. In this case they are never set 

 free from the gametangia, but the walls of the latter coalesce and 

 fusion takes place inside the structure so formed, a zygospore 

 being the result [fig. 820). These isogamous fungi form the 

 group of the Zygomycetes. 



In other cases both male and 

 female gametes are found. The 

 female is usually an oosphere, 

 contained either singly or in 

 numbers inside a structure that 

 may be called an oogonium {fig. 

 821). In this case the male 

 usually consists of a mass of 

 naked protoplasm, which occurs 

 in a special branch of one of 

 the hyphse, in close proximity 

 to the oogonium. This branch 

 is known as & pollinodium {fig. 

 821, a7i). In another section the 

 male gametes are differentiated 

 and are set free. They are small 

 rounded cells, clothed with a cell- 

 wall, and known as spermatia. 

 They are produced hy abstriction 

 from the apex of a special filament, 

 the sterig77ia, a number of these 

 being developed in a special re- 

 ceptacle, the spermogonium. The 

 female organ, which is knowTi as 

 an archicarj) (fig. 783), contains 

 no differentiated female cell, and 

 corresponds to the procarpiura of 

 the Ehodophyceae. This some- 

 times has a trichogyne, as in the latter group. 



In some forms which bear an archicarp the male cell is not 

 differentiated either, but is much like the gamete of the group 

 last mentioned, being produced by a hypha close to the 

 archicarp. The product of fertilisation in the last two cases is 

 known as an ascocarp, and is the sporophj^te of the plant. 



The spores or gonidia of fmigi are borne in great numbers, and 

 receive different names according to the organs in or on which 



F?r/.820. Conjugation in Mucor Mucedo. 

 h. Two hyphae which have come 

 into contact at their apices, and each 

 lias cut off from itself a cell. xiig. 

 Zygospore resulting from the fusion 

 of these cells. zyg\ Adult zygospore 

 after germination, p. Promycelium 

 bearing a sporangium sp. 



