may be prevented from attaining a normal size, and when bad] 
¥ a 
v 
5 
fested they become more or less curled, with the convex side wu - 
most. On the upper surface of leaves of Vitis vinifera and its vari 
ties, however, the disease shows not in any discolorations, but oppo- 
site the spots beneath there are conspicuously raised areas imparting 
to the surface a blistered appearance. This results from a greater 
growth or multiplication of cells in the diseased areas than in the 
surrounding unaffected portions. — 
(c) MINUTE CHARACTERS (Fig. 1). : oi ie 
If the lustrous white, or later yellowish, spots are examined with a 
a good lens or magnifying glass they will appear to be composed of a ~~ 
e. 
dense growth of shining hairs (Fig. 1, a, a), with somewhat enlarged ~~ 
tips, and this is their true character, as may be determined by ami- ~~ 
croscopical examination. There is no longer any danger of mistak- ~~ 
ing these hair-like growths for the downy mildew, for when viewed _ 
under the microscope there is not even the slightest resemblance be- | 
tween them, as may be seen by comparing Fig. 2, Plate XVII, of this 
report, with Fig. 10, Plate I, inthe annual report for 1886. Inthefor- . ~ 
mer figure, which illustrates a transverse section through one of the 
spots affected with Erinose, the microscopical characters of the dis- 
ease are illustrated. The cells composing the tissues of the leaf are. 
seen to be abnormal in their development, while the epidermal cellsof — ~ 
the lower surface are elongated into hair-like projections, sometintes ~~ 
branched above, and with rounded and more or less club-shaped tips. 
The cause of this abnormal growth is the Acarid, two specimens of © — 
which (Fig. 2, b b) are shown in the figure equally magnified with~= ~ 
the section. To the naked eye they are barely visible, even when ~ 
placed upon a surface of contrasting color; it is quite impossible to ; 
detect them on the spots without a good magnifying glass. . These 
parasites puncture the epidermal cells of the leaf, from the irritating | 
or poisoning effects of which the abnormal growths and consequent . ~ 
spots are developed. Bye 
Phytoptus vitis lives mostly in the larval state, the condition illus- 
trated in our figure. The adult stage is found only in the spring, ~~ 
and then but for a brief period. When it comes out of theegg it. . 
possesses four feet, situated upon the anterior part of the body, which = 
is composed of several rings; the skin is striated and furnished with 
four stiff hairs upon each side of the body, and two long bristles are 
fixed in the posterior extremity.. The larve multiply during the ~~ 
summer by means of parthenogenetic eggs (Fig. 2, c}). Attheap- 
proach of winter they become encysted and hibernate under the — 
scales of the buds or in crevices of the bark. In the spring the cysts ~~ 
are ruptured and from them come six-footed larvee, which soon 
develop two additional feet, thus passing into the mature stage. | 
The adults die immediately after the eggs are laid, the latter giving ~ 
rise to the four-footed larvee above described.* af 
(d) DISTRIBUTION, EFFECTS, AND TREATMENT. 
Hrinose is widely distributed throughout the country, and may be 
looked for wherever the vine is cultivated. Wehave seenitinNew | 
Jersey, District of Columbia, Texas, and California. itis nowhere — 
particularly injurious, and only in very rare cases does it ever make — 
*P, Viala, ‘ Les Maladies de la Vigne,” p. 451. 
