tfue state of affairs which, briefly, is that the froft-like, downy growth 

 seen on the under side of the leaf is in reality a dense frost of exceed- 

 ly delicate, colourless threads branching near the top like trees and bear- 

 ing upon the tips of ihese branches egg-shaped bodies of the same gene- 

 eral colour and structure as the branches themselves. Further examina- 

 tion shows that these little tree-shaped bodies extend down into the 

 very heart of the leaf and that they are there provided with delicate 

 branching threads which may, for the sake of comparison, be likened 

 to rootlets. The delicate threads are found creeping through the leaf in 

 all directions, and, as far as they extend, the sap of the latter is destroy- 

 ed. Destruction is as complete in this case as if it had been effected by 

 heat, cold, or any other mean.^. That the mildew is the real cau?e of 

 this change in the leaf cannot be doubted. 



Let us now go a little further and see what it is doing with the food 

 for such it is, that it obtaiued from the vine. By means of suckers 

 with which the minute threads already mentioned are provided, the 

 juices which form the most vital part of the leaf are absorbed and used 

 in building up the tree-like stems, branches, and other parts of the fun- 

 gus. In other words, while the roots and green parts of the vine are 

 actively at work obtaining materials from the soil and air out of which 

 it is building up its own body, this insidious robber, the mildew, is 

 stealing the material for its own benefit. If mildew were forced 

 to go to the soil and air for its food it would die, and this is why 

 it is called a parasite, having, as it does, to depend for its nourishment 

 on material already prepared for it. That the mildew is a true plant 

 has already been noted, but a closer study of it brings out 

 this fact more strikingly. The egg-shaped bodies already mentioned 

 as occurring on the ends of the branches borne on rhe under 

 side of the leaf are in reality reproductive organs analogous to seeds. 

 These bodies quickly fall from their attachments and being exceed- 

 ingly light they are easily carried about by winds and other agents. 



Whenever they come in contact with healthy vine leaves and the 

 proper conditions of moisture and heat are present they germinate and 

 eventually give rise to another crop of branches, root-like threads, etc., 

 like those already mentioned. In warm, damp weather it requires only 

 a few dnys to perfect a crop of the repro luctive bodies, or spores, and 

 this often accounts for the rapid spread of the disease. At the first frost 

 the delicate exposed portions of the fungus are killed, but in the mean- 

 time another kind of reproductive body has formed inside of the leaf, 

 where it is protected from cold. When the foliage falls in autumn 

 these bodies fall with it and remain safely-hidden away until the follow- 

 ing spring or summer, when they are set free by the decay of the leaf. 

 At thi? time it is supposed that they germinate and give rise to the frost- 

 like patches already described. This completes the life cycle, which in 

 all of its details is almost as complicated as that of the grape itself. 



We believe now the fact that fungi are true plants has been made 

 clear. Further, it is hoped that what has been said about the manner, 

 in which the grape vine downy mildew lives and produces disease will, 

 make this part of the subject understood. It is only necessary now to 

 say a few words in regard to the number of fungi affecting plants and 

 the extent of the injuries they occasion before taking up the 



