1882.] FUNGI INJURIOUS TO VEGETATION. 173 



confine itself to the leaves, but works in the young stems, causing 

 them to take on strange shapes and unnatural colors, and to finally 

 wither, turn brown, and at last die. 



This pest, though somewhat difi:erent in its manner of growth, 

 is a close relative of the black knot, which has proved so destruc- 

 tive to the plum and cherry trees. The black knot is a much more 

 conspicuous parasite than the peach curl, as it works almost en- 

 tirely upon the stems, and even large branches, and becomes very 

 noticeable from the distortions and black color which the branches 

 assume. The only remedy for the "curl" is the knife. All the 

 branches, with their leaves, which are affected, should be cut off 

 and burned. The disease is propagated by means of small spores 

 that are found in the leaves later in the season, and by burning 

 they are destroyed. The peach "curl" is easily seen when once 

 the eye is trained for it, and an orchard, unless it is badly affected, 

 can be gone over quite rapidly, and the diseased parts removed. 

 There is no doubt that it is injurious, and it is also evident that 

 unless means are taken to keep it in check the trouble may in- 

 crease, and in time become a serious matter in the peach orchards. 

 Those who have had their plum orchards ruined by the black 

 knot know something of the way in which a fungus can destroy 

 valuable fruit trees. The peach "curl" belongs to the same 

 destructive class. 



The American Grape Mildew. 



In order to become more thoroughly acquainted with the preva- 

 lence of grape mildew, the writer, in the summer of 1877, sent a 

 list of questions to the leading grape-growers in the country. 

 From the 'replies, many of which were very full, it was evident that 

 in the mildew the grape-growers have a serious and destructive pest. 

 The literature of the subject shows that it is no new thing, and 

 that grape mildew has received considerable attention from horti- 

 cultural writers. The mildew is a minute fungus, known to bota- 

 nists as Peronospora viticola. This fungus is best observed on the 

 leaves, where it makes yellowish-brown patches on the upper side, 

 while beneath there is a white forest of the spores. The smooth- 

 leaved varieties show the mildew to the best advantage, as it is not 

 obscured by the dense growth of hairs of the " woolly " varieties. 

 The threads of the fungus run in all directions between the cells 

 of the leaf, and after a short time reach the breathing spores, or 

 stomata. The threads of the fungus pass out, and reach the air, 



