dha 
With the second group of injurious mites this paper has chiefly 
to do. The peculiar detormities to which many of them give rise 
were placed by the earlier botanists among fungi, chiefly in the 
genera Erineum and Phyllerium, and the disease at that time was 
called eriniosis. In 1737 a French naturalist, Reaumur, found, in 
an abnormal growth on the linden, a minute worm-like «animal, 
which he thought gave rise to the abnormal formations on the 
leaves. This animal was determined, by a later French entomolo- 
gist (Dugés) to be a mite, and it received from him the generic name 
Phytoptus, from its plant-infesting habits. Since then, others of 
these growths have been traced to their causes, and at present a 
long list of plants may be given, each of which has its peculiar 
Phytoptus. The growths are now called by specialists, cecidii, or, 
more exactly, acaro-cecidw. 
The growths to which the Phytopti give rise are not always what 
would be called galls; and in some cases they do not produce growths 
of any kind, but live in the buds in such numbers that the latter 
never develop, but remain blackened and swollen. Besides swellings 
of the leaf substance called gails, the attacks of some of these 
mites give rise to dense mats of twisted hairs on the under side of 
leaves; and in the midst of these groves the mites live and propo- 
gate. These hairs differ very little in character from the ordinary 
hairs of the plant, being sometimes single and again many-celled, 
but the occurrence in dense groves and the frequent strange forms 
which they assume will ordinarily distinguish them from the normal 
hairs of the plant. Some of the forms of these hairs may be worth 
indicating. A common one is what may be called club-shaped, the 
hair being slender towards the leaf, and expanding slightly towards 
the extremity. Others of the hairs expand more abruptly outwards, 
and are quite short, being thus knob-hke. Occasionally one occurs 
that gives off a lateral shoot, and often most of the hairs consti- 
tuting a grove are irregularly twisted. The usual form is, however, 
very nearly that of the scattered hairs which may be found on other 
parts of the plant. The patches of these hairs are at first white, 
but when old assume a rusty-brown color very like that of some of 
the fungi known as rusts. At this stage few mites will be found in 
the growths, the brown color of the hairs being due to their having 
been exhausted and dried up. 
