130 TRANSACTIONS OF THE [Sess, LXXxv. 
Loesener (7), Schumann (8), Ludwig (9), Magoezy-Dietz 
(10), Penzig and Chabrera (11), Guerin (12), Delpino (13), 
and Rocchetti (14) have shown that these shelters exist in 
the following natural orders, viz.: Melastomacez, Meni- 
spermacee, Euphorbiacez, Piperaceze, Dipterocarpee, Thy- 
melez, Styracaceze, Simarubez, and especially in Lauraceze 
and Rubiacez. The last-mentioned author has a list of 
270 acarophilous species. 
Moreover, many plants which are regularly visited or 
inhabited by mites are without anything that one can call 
an acarodomatium. The mites take up residence in any 
convenient nook or cranny, and one cannot say that these 
crevices are specially produced for the good of the mites. 
Thus many forest trees have holes in the trunk where 
some branch has decayed away, and birds such as the 
titmouse nest in holes of this kind. Titmice are very 
useful to the trees, and find these hollows very convenient, 
but the holes were not formed for the good of the titmouse, 
although this bird is one of the most useful of British 
species. 
When one reflects on the multitude of mites visiting 
regularly so many plants, it is impossible not to speculate as 
to what is their part in the general economy of plant life. 
Lundstrom suggested that they kept the leaves free of 
dangerous fungi and insects. 
It is well known that in tropical and subtropical countries 
many plants are subject to the attacks of leaf-epiphytes. 
It is quite common to find leaves entirely covered by a 
heterogeneous vegetation of alge, lichens, mosses, and 
liverworts. Stahl has figured the leaf of a Medinilla so 
overgrown by an epiphytic vegetation of this kind that it 
must have been impossible for it to carry on its functions. 
Such leaf-epiphytes are exceedingly common in many 
vegetation formations in the tropics. 
Now, most of Lundstrom’s mite-plants belong to certain 
districts in South America. Malme some time afterwards 
visited the same locality. He found that in these light 
woods known as “Capoes” smooth-leaved shrubs were 
infested with these epiphytes, but that the acarophilous 
plants with acarodomatia were much less or not at all 
affected. Penziy and Chabrera confirm this observation. 
