INTRODUCTION. 



etc., they live parasitically on living or dead organisms, 

 thereby obtaining the required albuminous substance 

 requisite to sustain life. 



Fungi living on dead or decaying organic matter are 

 termed saprophytes ; others infesting living plants, caus- 

 ing more or less serious disease in the host, are termed 

 parasites. 



According to Dr. Sieber {Journal filr Praktische 

 Chemie [2], 23, p. 412) certain pommon mildews have the 

 following compositions : — • 



The analyses show that mildews contain a considerable 

 percentage of albumin, derived in the first instance from 

 the host-plant upon which the parasites live. The host- 

 plant thereby becomes diseased, and its vitality is greatly 

 impaired. The vitality of the spores of most fungi is very 

 considerable ; and the spores are capable of being dried 

 up in the dust of the atmosphere for months, and it may 

 be years, without losing their vitality. 



So far, we have spoken in a general way of the struc- 

 ture, etc., of the vegetable foes which are injurious to 

 farm crops. We now offer a few remarks concerning 

 those members of the animal kingdom which are un- 

 doubtedly the foes of the farm. 



