MILDEW AND BRAND. 55 



As the same Puccmia is also to be found on 

 numerous grasses, no prudent farmer will permit 

 these to luxuriate around the borders of his fields, 

 lest they should serve to introduce or increase the 

 pest he so much dreads. 



The germination of the spores of the corn mil- 

 dew is a very interesting and instructive process, 

 which may be observed with a very little trouble. 

 If the spores be scraped from the sori of the pre- 

 ceding year (we are not sure that those of the 

 current year will succeed), and kept for a short time 

 in a damp atmosphere under a glass receiver, 

 minute colourless threads will be seen to issue both 

 from the upper and lower divisions of the spores. 

 These will attain a length several times that of the 

 spores from whence they spring. The extremities 

 of these threads ultimately thicken, and two or 

 three septse are formed across each, dividing it 

 into cells, in which a little orange-coloured endo- 

 chrome accumulates. From the walls of each of 

 these cells, or joints, a small pedicel, or spicule, is 

 produced outwards, the tip of which gradually 

 swells until a spherical head is formed, into which 

 the orange-coloured fluid passes from the extremi- 

 ties of the threads.* A quantity of such threads, 

 bearing at their summits from one to four of these 

 orange-coloured, spherical, secondary fruits, supply 



* Similar in all essential particulars tc the germination of 

 Aregma (plate III. fig. 45). 



