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cross in some instances. From these cross-fertilizations seed has 
been obtained, and the result of their cultivation will be awaited with 
interest. — Gardeners Chronicle. 
Variations in Quercus prinoides. — At a meeting of the Philadelphia 
Academy of Natural Sciences, August 4th, Mr. Meehan exhibited a 
series of fruiting specimens of branches of Quercus prinoides. In 
some, the leaves were almost orbicular and obtuse, in others narrowly 
lanceolate or saliciform and acute, others had lobed and wavy 
edges, while others were quite entire. The plants were all growing 
within a few feet of each other, and the parent plants were also all 
under the same conditions of environment, and were all at no distant 
date from one parentage. 
They were exhibited, said Mr. Meehan, for two purposes — first 
to show that what was commonly understood as environment was not 
a main factor in the origination of variation, and secondly to show 
that variation was independent also of. mere conditions of growth or 
sexual peculiarities to which variation was sometimes referred. It was 
indeed true that young plants often had leaves varying from those on 
the older plants, and plants or branches bearing flowers of one sex 
would have characters varying from those of another sex, but these 
specimens were all fertile, and with young acorns. There was no 
possible ground for any suggestion as to different conditions in any 
sense, and the variations could be attributed only to an innate and 
wholly unknown power to vary, which science had so far been unable 
to reach. 
Sonora Gum.-~A substance called " Sonora gum," somewhat re- 
sembling a gum-resin in external appearance, and of hitherto uncer- 
tain origin, is found sparingly in commerce in California, and is used 
by brewers there in the manufacture of porter. Upon an investiga- 
tion of the matter, Mr. F. Grazer finds that this so-called gum is the 
exudation from the branches of Larrea Mexicana, which was referred 
to under the title of Arizona shellac in a paper read by Professor 
Stillman at a meeting of the California Academy of Sciences several 
years ago. Mr. B. B. Redding, at the same meeting, referred to the 
plant as a source from which our commercial shellac could be obtained, 
stating that these lac-yielding plants, including Acacia Greggii, were 
as plentiful as the so-called sage-brush, from Southern Utah to New 
Mexico, and from the Colorado desert to Western Texas, the lac 
being inost abundant around stations on the Mojave and Colorado 
deserts. The exudation, which takes place as the result of an msect s 
sting, could be easily collected by boiling the twigs in water, the 
gum (?) which rises to the top being skimmed off, stramed, and dried 
on smooth stones, and hand-pressed into flakes, ready to make seahng 
wax or varnish. The plant requires a rainfall of three inches a year. 
Formation of Gum in Trees.—Some time since Sir James Paget 
created considerable interest by quoting m one of his lectures the 
results of an investigation" by Dr. Beijerinck mto the cause of the 
formation of gum in trees, which led him to believe that it was due to 
a pathological change brought about by the influence of a fungus 
(BuLLETiS, xi., 33). Working quite independently, and m ignorance 
of Dr. Beiierinck's researches, Dr. Wiesner has since arrived at a sim- 
