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. 



FIG. 15. Typical forms of basidia, with spores in the Basidio- 

 mycetes. i, Tulostoma mammosum; 2, Dacromyces deliquescens ; 



3, basidia with spores, and cystidia of Peniophora inconspicna ; 



4, bisporous basidia of Lycoperdon echinatum ; 5, two spores of same 

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

 of hymenium of a typical agaric, Inocvbe asterospera, with basidia, 

 bearing spores, cystidia, or sterile basidia, and elongated cystidia. 

 All highly mag. 



There is much difference of opinion as to the exact 

 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 



