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STRANGE DEVELOPMENTS OF STOMATA ON CARYA ALBA CAUSED 
BY PHYLLOXERA.* 
By D. A. OWEN, Franklin, Ind. 
The stomata or breathing pores of Carya alba are naturally all devel- 
oped upon the lower epidermis of the leaf. But, owing to the oviposit- 
ing of the Phylloxera in the leaf through the lower epidermis, there is 
developed upon the upper side a hemispherical gall. This gall, like all 
other galls, is the nest of the insects, and in due time the young of the 
Phylloxera may be seen issuing from a slit upon the lower side of the 
leaf. 
Upon the lower epidermis, beneath the gall, may be seen a changed 
form of cell structure in which there are to be found in almost every case 
no stomata. But upon the upper side of the gall there are stomata in- 
variably found, but not in as great abundance as are found upon the 
lower epidermis of a normal leaf. 
In and around the opening of the gall there are to be found numerous 
single-celled hairs, all of which point outwards, as if guarding the ovum 
and young from the ravages of an enemy. _ 
That which remains yet to be solved is: For what purpose are these 
stomata developed upon the upper side of the gall? Does the plant 
develop these trichomes for its own use, or for the protection of the in- 
sect? Is the insect injurious or beneficial to the plant? 
It is hoped future investigations will solve some of these problems. 
EXTRACTS FROM CORRESPONDENCE. 
Destruction of Plant-lice in the Egg State. 
Do you think it practicable to destroy the eggs of the Aphis by spraying any sub- 
stance on the tree or shrub during the latter part of the winter? I have tried kero- 
- sene in various strengths up to 30 per cent, and it does not dothe work. I have been 
experimenting in the hope of finding something that will dissolve the shell of the 
egg, but find it extremely resistant, scarcely yielding to the strongest acids and alka- 
lies. Ihave been advised to try some of the fixatives that entomologists use for 
staining chitine, but nothing that I have tried appears to penetrate the shell at all, 
so far as I can determine with the microscope. Please tell me if any experiments 
have been made in this line, and if you would advise me to continue my investiga- 
tions.—[E. 8S. Goff, Wisconsin, March 10, 1892. ‘ 
REPLY.—I donot think that you will find any substance that will destroy the egg 
of plant-lice as effectually as will the kerosene emulsion. I think it more than prob- 
able that you will find that the eggs which you have treated, though they may show 
signs of life, will not hatch. My past experience would indicate that the eggs of 
plant-lice when thoroughly sprayed with kerosene-soap emulsion did not hatch, and 
* Read before the Indiana Academy of Sciences, December 30, 1891. 
