264 STATE HORTICULTURAL SOCIETY. 



m a damp place, covering it with their fine white filaments and brown or black 

 spore-bearing heads. Though often troublesome intruders when they fasten in 

 this way upon our stores of provisions, the brown moulds are really friends in 

 disguise, acting as so many scavengers to clear away material that would other- 

 wise become unwholesome. 



THE WUITK MOULDS.. 



A second class of fungi includes the white moulds that are found in the form 

 of delicate tults of fine white filaments, chiefly on the surface of leaves, but 

 not uncommonly occurring on the fresh shoots and other green parts of living 

 plants. Some of tlie most destructive fungi are included in this class, known 

 by the scientific name Peronosporece, among which may be specially mentioned 

 the potato fungus tiiat from time to time has been the occasion of the loss of 

 the potato crop in Ireland; the onion mould, sometimes very common and destruc- 

 tive to young onion plants ; another species growing upon and destroying culti- 

 vated turnips, and still others on parsnips, peas, and other crops. The single 

 species occurring in this country upon a woody plant is Pero)Wspora viticola or 

 the grape-vine mildew. The fungus in question appears on the under surface 

 of grai)e leaves of both indigenous and cultivated species as a fine, white, frosty- 

 looking growth, recognized under tlie microscope as a multitude of delicate 

 filaments producing at their tips an abundance of spores. The spores readily 

 germinate under proper conditions of warmth and moisture, and thus secure 

 the rapid multiplication of the fungus and consequent spread of the disease. 

 Later in the season, larger and darker colored spores with a tliick wall are pro- 

 •duced inside the tissues of the leaf and fall with it to the ground in the 

 autumn. Under the influence of the fungus the leaves dry and curl up, become • 

 •discolored and brittle, and though they remain upon the vine for some time, 

 they are unable to perform their proper functions of respiration and assimila- 

 tion. The fungus, therefore, is the exciting cause of an unhealthy or diseased 

 condition of the vine, and should be treated as such. It appears that no great 

 amount of injury has yet been reported from its presence uj)on grape vines in 

 the United States, but it has already proved highly injurious to American 

 vines cultivated in Europe, and especially in Algiers; and according to Dr. 

 Englemann it has occasioned some trouble in Missouri, where it begins earl^' in 

 the summer and attacks not only the leaves, but the young berries and their 

 stems. It occurs quite commonly at Ann Arbor on both cultivated and wild 

 grapevines; but there are no reports here of its having been the occasion of any 

 injurious effects. The fact that the resting spores which carry the fungus 

 through the winter are produced within the tissue of the leaf, and remain there 

 «ntil set free by its rotting or cracking open, suggests the gathering in the 

 autumn and burning of the leaves of all vines that liavt; shown the presence of 

 the disease, as being the most certain means of preventing its spreading the 

 following year. 



A disease known as "grape rot" has in some years prevailed extensively ou 

 the islands in Lake Erie, comprising Put-in-B.iy township, lying to the east- 

 ward of Toledo, and has also been reported in Southern Michigan. According' 

 to the statements of those who have had most experience with the disease, it 

 never occurs except with low state of barometer and humid atmosphere. The 

 berry, whieii is attacked "at an}' time from the blossom well up to Hiaturity," 

 pres«'nt8 at first a grayish, mottled appearance, and afterwards becomes black 

 and rotten. The disease is reported as sometimes occuring half a dozen times 

 during the season, and uniformly in "muggy" weather. "The section of 



