Dec. 1910.] BOTANICAL SOCIETY OF EDINBURGH 127 
On the under side of almost any leaf of any of our common 
trees there are to be found tufts of hairs, often at the angle 
where a side vein joins the midrib. The small hollows 
behind the hairs are the homes and shelters of the mites, 
and have been called acarodomatia. Within the little 
angle where the side vein branches off, there is often a 
curiously intricate and complex little cavern reaching up 
into the tissue, and guarded by a sort of chevauax-de-frise 
of special trichomes. 
I have tried to draw sections of these little caves, but 
gave up the attempt in despair, for they are very difficult 
to section and are almost impossible to draw. 
During the day, the mites pass their time in these caverns. 
If disturbed, they come out with every appearance of irrita- 
tion and run about with extraordinary quickness, or, as 
Lundstrom says, with “ unglaublicher Schnelligkeit.”. They 
are strictly nocturnal, like so many other beasts of prey, 
and object to being exhibited in daylight. 
As the summer goes on, they seem to get more and more 
numerous, and they are especially abundant in September ; 
but when the leaves begin to dry up, and the little hairs 
which guard the entrances of their shelters shrivel away, 
some of the mites abandon the leaves altogether and appear 
to take refuge in crannies of the bark, in the bud-scales, 
often in the fruit, and sometimes even on the seed itself. 
It has been found that, when such seeds are sown, the 
mites infect the seedling leaves as soon as these are 
sufficiently mature. 
I am by no means sure that all the mites abandon the 
leaves before the latter fall in autumn. I suspect that 
many winter in leaf-mould, but only a skilled entomologist 
could decide such questions. On the bramble in spring I 
have found mites still active on last year’s leaves when the 
new leaves were just ready to be infected. I have also 
found them in the lenticels of an oak and on the cut end of 
a pear twig.! 
It is clear, however, that there is no difficulty about the 
succession of mites from year to year. 
In the summer the number of these mites is extra- 
1 These may not have been the mites which inhabit the leaves in 
summer. 
TRANS, BOT. SOC, EDIN. VOL. XXIV. 10 
