58 DISEASES OF CROPS. 



ing a kind of " head " with one or more lacunse (apertures). 

 The mature spores rupture the " skin " of plant potato and 

 are therefore liberated. 



Prevention and Cure. — (1) The seed potatoes should be 

 free from this disease. (2) Steep the seed potatoes in a 

 solution containing from 1 to 5 per cent, of iron sulphate. 

 This will destroy any spores of the potato smut that may 

 be upon them. 



Fusisporium solani {Periola tomentosa, Fig. 24) 

 is another fungus which attacks potato crops. It makes 



Fig. 24. — FusispoKinii solani of Potatoes. 

 ( X 200 aiam.) 



its appearance chiefly in the autumn, when it is to be 

 seen upon the potatoes growing in the soils of the sotith- 

 ern and midland counties. So far, it has confined its 

 attacks to these covinties, and has not been discovered in 

 Wales or Scotland. Fusisporium solani attacks chiefly 

 the starch granules of the tuber by sending its mycelium 

 amongst the cells, and thereby causes putrefaction. The 

 mycelium, in a few hours, gives rise to conidiophores, 

 being crescent-shaped compound conidia (spores) (Fig. 

 24 B). The spores, which are divided by three transverse 

 septa, separate when mature (Fig. 24 C), forming four 

 more or less square-ended spores. These subsequently 



