BASIDIOMYCETES 441 



A further point of importance is that in a nutritive liquid, like the 

 foul water of the manure-heap, the spores formed on germination 

 continue to multiply by budding, thus increasing the chances of 

 infection (Fig. 339, d, e). The detached spores then conjugate and 

 begin a bi-nucleate stage, which is able to penetrate the tissue of the 

 seedling corn but not of the adult. The plant, once infected, grows on 

 as though quite healthy till the flowering period. Then the parasite, 

 the mycelium of which has followed its growth internally, fastens on 

 the ovary where nutritive material is concentrated, and diverts the 

 food from the formation of the grain to the nutrition of a mass of its 

 own spores. For prevention of the disease " dressing " of the seed- 

 grain with disinfecting mixtures is practised. But equally important 

 is to prevent the manure being contaminated by the spores from 

 the smutted crop of a previous year. 



Hymenomycetales. 



The life-history of the Rust of Wheat has been described in some 

 detail as giving an example of a Basidiomycete which still shows 



Fig. 340. 



Fomes igniarius. Section through an old fructification, showing annual zones 

 of growth, a = point of attachment upon the tree which is its host. The porous 

 hymenium is directed downwards, (h nat. size.) (From Strasburger.) 



evidence of sexuality, both morphologically and physiologically ; 

 though it is altered from what was probably its normal and original 

 course. In the rest of the Basidiomycetes such evidence is wanting. 

 They may provisionally be held to be saprophytes and parasites which 

 were descended from an ancestry with normal sexuality, but have 

 advanced further in the elimination of their sexual process. In some 

 species variation is ensured by the association of myeelia of different 

 origin. The basidia (Fig. 328) are borne on fruit-bodies, which are 

 often large and brightly coloured. They arise from a mycelium 

 which acquires the necessary nourishment sometimes parasitically 

 but more often from saprophytic sources. The basidia are borne in 

 various ways, and this gives distinctive characters to the main groups 



