8 4 



DISEASES OF CULTIVATED PLANTS 



As a rule a basidium bears four spores at its apex. There 

 are two important groups, Agaricaceae and Gasteromycetaceae. 

 In the former, represented by mushrooms and toadstools, the 

 basidia are borne on the gills, whereas in the Gastero- 

 mycetaceae, including puffballs, stinkhorn, etc., the spore- 

 bearing portion is at first concealed in a membrane or volva. 



mrr 



1 m 



Fig. 15. Typical forms <>f basidia, with spores in the Basidio- 

 mycetes. 1, Tvlostotna mammosum \ 2, Dacromycei deliquesce* s\ 



3, basidia will tid cystidia of Peniophora inconspicua ; 



4, bisporous basidia chinatum ; 5, two spores of same 

 showing persistent sterigmata ; 6, Scleroderma vulgare; 7, portion 

 of hymenium of a typical agaric, Inocybe asterosfera, with basidia, 



bearing s| ystidia, 01 sterile basidia, and elongated cystidia. 



All highly mag. 



There is much difference of opinion as to the r\act 



position, in the sequence of evolution, of the two important 

 families, Ustilaginaceae smuts and bunts of cereals, etc. and 

 the Uredinaceae rusts and mildews of cereals and other 

 plants. In the latter group heteroecism is rampant. The 

 members of both groups are almost without exception 



