1880.] On the Origin of the Lac. 785 
above quoted from “ Chambers’ Encyclopedia,” Eye-witnesses 
say, that the Arizona lac also does not occur wherever the plant, 
upon which it grows, is found, but only in particular regions or 
patches. In the second place the gum-lac of India occurs on no 
less than five trees, Ficus religiosa, Ficus indica, Rhamnus jujuba, 
Croton lacciferum, Butea frondosa, and that from Arizona on two 
plants, the Larrea mexicana and Acacia greggt. These plants are 
not related for the most part, and do not afford the gum except 
under the influence of the insect. 
In explanation of these facts we have two alternatives to choose 
from. First, the gum is an exudation from the twig, excited by 
the puncture of the Coccus; it flows out, envelops the insects, 
hardens and forms the gum-lacs; or, second, that the gum ts the 
elaboration of the insect itself. : 
he first explanation is the one usually given, the second one 
appears to me the true one, and the following facts and consid- 
erations appear to me to sustain this view: 
1. The gum-lac is not simple, like most vegetable resins, but — 
is composed of resins soluble in alcohol, wax and gluten, or 
substances resembling gluten. Such a complex substance might 
be expected from an animal secretion. 
2. The resin, as far as known, possesses the same general com- 
position and properties independent of the species of plant, whence 
it is derived, since no specific difference is given for any of the 
seven India varieties, and the two Arizona sorts have probably- 
the same general composition. The kind of plant and the char- 
acter of its juices undoubtedly have a general influence, inasmuch 
as the sap of some plants would not support the life of the insect 
nor furnish it its necessary materials for the elaboration of its 
products. 
3. If the resin were an exudation from the plant, simply — = 
induced by the puncture, we should expect to find this resin more 
or less collected into globules, drops, or masses independent of 
the immediate presence of the insect. In my examination es 
could find no particle of resin which did not form a bounding 
wall to one or more of these cells occupied by the egg-sacs. 
The only places, where the resin anpeared solid and thick, was i 
in the spaces between three or more contiguous cells, as if the 
sacs had, by their united secretions, filled up the small room be- 
tween them. In some specimens what appeared to be a small 
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