JUNE 4, 1923 PROCEEDINGS: BIOLOGICAL SOCIETY 237 
Dr. Huan M. Smirx gave some notes on the flowering of Cercis. 
F. V. CovinuE: The effect of aluminum sulphate on rhododendron seedlings. 
Rhododendrons do not thrive in ordinary fertile garden or greenhouse soil, 
but they grow with great luxuriance in sand mixed with peat, with rotting 
wood, or with half-rotted leaves. Although both these types of soil con- 
tain an abundance of plant food, the rhododendrons thrive in the peat and 
sand mixture because its chemical reaction is acid, and they die in the or- 
dinary fertile garden soil because its reaction is neutral or alkaline. Experi- 
ments begun in March, 1921, show that the application of aluminum sul- 
phate to ordinary fertile garden or greenhouse soil changes its reaction from 
neutral or alkaline to acid, and that after this treatment rhododendrons 
will thrive in it almost as well as in a natural acid soil of peat and sand. 
The paper will be published in full as Bulletin 1 of the newly formed Ameri- 
can Horticultural Society, Washington, D. C. 
PERLEY SPAULDING: The biology of Pinus strobus. The speaker gave 
notes on Pinus strobus as seen in Europe only. It is essentially an orna- 
mental except for small areas of forest in Switzerland, eastern France and 
Germany. ‘The blister rust caused by Cronartium ribicola is its worst enemy 
and is exterminating the species in Europe, as reforestation with it is dis- 
continued. Where the blister rust has not attacked it, its timber produc- 
tion is of high value. Rabbits prevent its reproduction naturally in Great 
Britain, by eating the young seedlings. Jays and squirrels feed on the 
seeds, limiting reproduction. Calcareous soils produce yellow-foliaged, 
sickly trees. The species is very hardy and quite free from snow breakage. 
Fomes annosus attacks it rarely. Peziza calycina occasionally attacks it. 
Armillaria mellea is a serious enemy especially on land previously occupied 
by hard wood species. 
J. M. Aupricu: The Canadian life zone as indicated by insect distribution. 
Of the three northern life zones recognized by Merriam and Bailey, the 
Canadian is the richest. It contains thousands of species of insects, no 
order being better represented than the Diptera. From the beginning it has 
proved difficult to fix the limits of the Canadian by any satisfactory list of 
typical plants or animals, the species generally shading off into the Transition 
or continuing up into the Hudsonian. The speaker found this difficulty also 
in the insects, citing numerous cases of species spreading beyond the true 
Canadian limits. A number of species of Diptera were cited which confirm 
in their appearance at points remote from each other the existence of a real 
life zone, though with vague boundaries. The scavenger flies were used to 
illustrate the subject further. 
H. C. Oseruotser: Notes on birds of the District of Columbia. The 
speaker mentioned a number of the rarer birds of the District of Columbia, 
illustrating his talk by colored lantern slides of the species discussed. 
650TH MEETING 
The 650th meeting was held in the auditorium of the Interior building 
March 14, 1923, at 8 p.m., jointly with Washington Academy of Sciences, 
the Geological Society, and the Botanical Society. The meeting was de- 
voted to a discussion of the fossil swamp deposit at the Walker Hotel site. 
The speakers were C. K. Wentworts, E. Brown, E. W. Berry, ALBERT 
Mann, and Laurence La Force. 
651ST MEETING 
The 651st meeting of the Biological Society was held in the lecture room 
of the Cosmos Club, March 17, 1923, at 8 p.m., with President Hircucock 
