FUNGI. 237 



Toe " of Turnips and other Cruciferous plants. It is 

 found in the roots, which become distorted and greatly 

 swollen by the absorption due to the fungus. If the 

 root is examined in July, the cells will be found filled 

 with the yellowish slimy protoplasm of the parasite. 

 Later on, in October, this has changed into multitudes 

 of little black spores very like grains of gunpowder. 

 When the turnip crop is lifted, the lower part of the 

 roots and very often the diseased plants are left lying 

 in the fields, or perhaps thrown against the side of the 

 hedge. These gradually decay, and the spores are 

 distributed by the wind or left lying in the soil. Next 

 year they germinate, and are able to search the soil for 

 Charlock or other Cruciferous weeds, on which they pass 

 their time until another turnip crop is grown, when 

 they will of course be quite ready to attack it. The 

 disease is naturally most prevalent in places where the 

 soil is damp. The application of lime is said to check 

 the spread of this fungus, but probably the destruction 

 of Charlock and other Cruciferous plants, and especially 

 the careful removal of all diseased turnips, would be 

 much more efficacious. 



It is obvious that the main importance of the Fungi 

 lies in their function of breaking up organic matter. 

 Even those which are parasitic are of use, as the 

 standard of efficiency for the species is maintained by 

 the destruction of the weaker individuals. There is 

 no very distinct border line between saprophytes and 

 parasites^ or indeed between the former and such species 

 as are in intimate association with the higher plants, 

 like the inycorhiza of trees. 



They are in all cases obviously a necessary group 

 of plants, and the study of them, though difficult, is 

 interesting, and is also of great value to agriculture. 



