GALLS CAUSED BY MITES 
103 
the other plants, with the result that the majority of their 
flowers were double, as well as those of isolated plants on 
which he had placed mites. He remarks: “ Veronica officinalis 
has only two stamens in each flower, and in the double 
flowers both these and the two carpels are changed into 
petals, so that of course we could not expect fruit and seeds 
from them. It would not be impossible, however, that 
flowers of other plant families, which are provided with a 
large number of stamens, might behave differently. It 
might happen, for example, that only some of the stamens 
would be changed into the petals by the gall-mites, and that 
the carpels would remain capable of fertilization. If on 
such plants fruits and seeds capable of germination should 
ripen, the latter might perhaps produce plants with com¬ 
pletely and half double flowers. This would be explained 
by supposing that the alteration undergone by the proto¬ 
plasm of the cells in the outer part of the flower had ex¬ 
tended to the inner, especially to the ovules and seeds, and, 
further, to the plants proceeding from these seeds. I would, 
therefore, not undertake to state that the Stocks ( Matthiola 
annua and incana ), the Wallflower ( Cheiranthus cheiri), the 
Pinks ( Dianthus caryophyllus , plumarius , etc.), the Poppies 
(Papaver Rhoeas and somnifernm), various Ranunculaceae 
( Delphinium , Poeonia, Ranunculus ), and many other plants 
which have long been cultivated in gardens with semi¬ 
double flowers, and which produce such flowers when pro¬ 
pagated by seeds, had not gained this characteristic in the 
first place by the influence of gall-mites.” 
Economic Notes 
Two species of mites cause much damage in fruit gardens. 
The more troublesome is probably the Black Currant gall - 
mite, Eriophyes ribis Nalepa. It was observed in this 
country at least sixty years ago, but it is only within recent 
years that it has spread rapidly and become a serious pest. 
These mites shelter in the buds over winter and migrate in 
