AGGRESSIVE PARASITISM OF FUNGI. 459 



ontmarslial those it seeks to destroy and rob of their treasures? Advantages 

 are seized upon, favorable conditions for the attack are improved, or in equal 

 ordinary combat swift and sure destruction follows the dread onslaught of the 

 parasitic hordes. 



Abundant evidence supports this idea. ^STumerous well-attested cases are at 

 hand, so that to one who examines carefully, and is prepared to properly esti- 

 mate the evidence before him, the conclusion is irresistible that the funffi do 

 cause disease in structures, which, but for their attacks, are healthy and vigor- 

 ous. When weakened by any cause, of course there is the more danger to the 

 debilitated party. In damp, dark weather, nnfavorable to general vegetation, 

 but well suited to fungous growth, the latter has the advantage, and is not 

 slow, as is well known, to improve the opportunity. Subject to some of the 

 varying conditions referred to in the first part of this paper, the following are 

 examples of diseases produced by fungous plants. In these cases, as in hosts 

 of others, it can be readily demonstrated that the parasites are the cause, not 

 simply the accompaniments, of the injury. 



Bunt, or Smut in Wheat, showing itself in the grain, and reducing the 

 whole interior to a black, pasty, or powdery mass. This is caused by the 

 spores of Tilletia caries being sown with the seed, and though not showing its 

 effects, the plant really grows with the wheat from the beginning. The prac- 

 tice of washing the seed in brine, and afterwards drying it with lime, is an 

 almost effectual preventive. Simple washing with water, or thoroughly 

 bloAving in the windmill, must aid. Rust of the stems and leaves of small 

 grains generally, but of wheat especially, is due to Fuccinia graminis, whose 

 spores form the rusty powder which is sometimes so abundant about harvest 

 time, staining the workmen's clothing. Another kind of spores are afterward 

 produced, which are nearly black. These last stick to the straw during the 

 winter, and doubtless constitute the germs of the next year's generation^ 

 Washing the seed can do no good in this case, while carefully carrying away 

 the straw, burning the stubble, and cleaning the corners of fences, etc., of all 

 grass-like productions, may prevent the attack. The full history of this para- 

 site has not been made out, but every farmer must have noticed that its growth 

 depends very largely upon the weather. Hot sunshine, broken at intervals by 

 showers of rain, load the air with vapor, rendering the atmosphere "muggy" 

 and iinsuited to ordinary vegetable growth, but well adapted to the Puccinia, 

 which quickly destroys the crop. It was present before, but not active enough 

 to become very injurious. 



The Rot of some stone fruits, causing them to shrivel upon the tree, and soon 

 covering them with a gray mass of dust, is the sure result of Oidium (Torula) 

 fructigenum. Any one may satisfy himself as to the action of this fungus by 

 simply w'etting or puncturing slightly the surface of a healthy fruit, and plac- 

 ing upon it some of the dust from an affected peach. The experiment is almost 

 sure to succeed, though occasionally, in dry, clear weather, it may miss.. 

 Examining with the microscope, twenty-four hours after the sowing, the sub- 

 stance of the fruit, the threads of the fungus, will be found in abundance, and 

 in two more days the unaided eye easily detects the mischievous work. Theo- 

 retically and practically the prevention of this disease is to ward off, as far as 

 possible, the insects which puncture the fruit, and to remove cautiously every 

 rotting one as soon as discovered. These may be buried in the ground or 

 burned. 



The Fire BVght of the pear needs more studv, but the Leaf Blight of pear 



