The Phytoptus of the Vine. By Prof. Giovanni Briosi. 183 
At present, however, after the observations of Fée, and the 
researches of Landois, Sorauer, Thomas, and others, it is ascer- 
tained beyond doubt that these cecidia are due to the punctures 
and irritation produced in the texture by the acarz, who lodge in 
it and live on the leaves. 
Cutting a very thin lamina across a gall of a vine leaf, and 
placing it under the microscope, there presents itself, as nearly as 
possible, a picture such as drawn in Fig. 14, viz. a forest of hairs 
of various sizes and shapes, and between these minute animals with 
elongated bodies, with four legs above, with small antenne, and 
segments precisely as Fée saw them in 1833.* 
These are mites (acar?), of which there has been formed a 
species for itself, called Phytoptus, which name was given to them 
in 1851 by Dujardin (who observed them on the linden and hazel), 
in order to express that they are really and solely parasites of 
living plants. These pathological plagues are thus produced. 
When the animal has found a favourable spot in the leaf, 
it pricks its texture, and sucks the moisture of the perforated 
cells. The plant now remedies on its part these punctures and 
prolonged irritation by supplying the wounded spot with fresh 
nourishment ; hence an afilux of substance (which can be ascer- 
tained under the microscope), and consequently an increase in the 
wounded cell or cells, which in consequence swell and extend 
externally and cause the formation of elevations. This process is 
clearly shown in Fig. 14, where f, e, d, are cells in various stages 
of such transformation. 
The cells participating in this work are solely the epidermoid 
cells. Professor Landois, of Heidelberg, to whom we are indebted 
for the most important and complete work on the Phytoptus vitis,t 
however, attributes these projections to the underlymg parenchy- 
matic cells, and says that the epidermoid cells are never trans- 
formed into projections (f), which is inexact.t 
These hairs or projections can attain a length four or five times 
the size of the leaf to which they belong; in fact, I found some 
of 0°85mm., 0°90 mm. (the average diameter of which was 
0:03 mm.), on a leaf which only had a thickness of 0°20 mm. 
They are generally club-shaped, that is, are thicker towards the 
upper end, especially when young ; they are more or less irregular, 
often crooked or curved in various ways, presenting protuberances 
* Feée attributed the formation of the galls “ to an elongated larva with four legs 
terminating in little tufts of hair, attached to the upper and fore part of the body, 
which has transverse rings, and is covered with hairs.” See Targioni Tozzetti, in the 
Bulletin of the Entomological Society of Italy, 1870, p. 283, and following ones. 
+ Summing up of Targioni in the Bulletin of the Italian Entomological 
Society, 1870, p. 283. 
t “ Die Epidermiszellen des Blattes wachsen nie zu Féden aus, sondern die Milbe 
sticht mit thren stiletartigen Mandibeln durch die Oberhaut die Parenchymzellen des 
Blattes an.’—Landois’ work, cited amongst the Publications, 
