192 -The Beneficial and Injurious Influences of Fungi. 



soil bacteria, have the power of fixing the atmospheric nitrogen 

 and storing it up in their roots- in the form of nodules, which 

 act beneficially on the following crops. This action of the 

 nitrifying bacteria is produced under the influence of the fungus 

 Rhizobium leguminosarum. 



The Leguminous plants develop these root tubercles most 

 readily in soil deficient in nitrogenous food substance and less 

 in soil rich in humus and nitrogenous matter. 



Virgil (b. B.C. 70), when writing on the cultivation of the 

 soil in his Georgics, Book I., is aware of the advantage of a 

 corn crop following a leguminous one when he says : 



' . . . . where, vetches, pulse, and tares have stood, 

 And stalks of lupines grew (a stubborn wood), 

 The ensuing season, in return, will bear 

 The bearded product of the golden year : ' 



Dryden's Translation. 



Having said so much for the good influences of Fungi, we 

 may now consider how they militate to the injury of mankind, 

 by lessening the food supply or by damaging its quality by 

 means of the many forms of plant diseases which go by the 

 names of smut, rust, mildew and blight in corn, canker and 

 rot in fruit, ' demic ' disease in potatoes, and many others so 

 well-known to farmers, gardeners and timber growers. 



The number of diseases to which human flesh is heir, 

 is exceeded by the number of diseases to which plants are liable ; 

 and as the study of human diseases has resulted in the allevi- 

 ating and in the prevention of much suffering and loss of life ; 

 so the study of the life history of these fungal diseases furnishes 

 us with the means of combating them, and thereby lessening 

 the loss on our corn and fruit crops and our timber supplies. 



Such knowledge empowers us with the means to receive 

 the most good from the hands of Nature and to avoid that 

 which might be injurious. 



It is not easy to estimate the world's annual loss from the 

 depredations of Fungi, but competent authorities are agreed 

 that the total loss caused by fungi to corn, fruit and timber 

 exceeds £300,000,000 per annum, much of which could be 

 averted by remedial measures. 



In this direction reference may be made to the statistics 

 issued by the Agricultural Department of the United States 

 where plant diseases are more studied than in any other part 

 of the world. 



The principal estimated losses recorded are as follows : — 

 The annual loss from Rust in Wheat ... ... £15,000,000 



,, ,, Potato Disease ... ... £7,000,000 



,, ,, Vine Disease in California £2,000,000 



,, Smut in Wheat ... ... £3,000,000 



,, Bitter-rot in Apples ... £2,000,000 



Naturalist, 



