206 Scientific News. [February, 
crystals perpendicular to the surface will be formed. Thus the 
wood contracting, and the ice expanding tangentially and longi- 
tudinally (chiefly the former), radial bursting is the result. The 
south side of a tree is the weakest, as more water exists there, 
and ice is first formed. Direct observation shows that the speci- 
fic gravity of sap is greater on the north side of a tree. 
Concentric splitting is explained by minute ice-crystals form- 
ing with their axes perpendicular to the wood-cylinder, thus 
causing radial tension. Want of ripeness of tissue, in the sense 
of the relation of water to other constituents, is the chief predis- 
posing cause. 
— Henry W. Beyerinck has, in the Botanische Zeitung, exam- 
ined the structure of the remarkable galls produced on the inter- 
nodes of the stem of Poa nemoralis by the attacks of Cecidomyia 
pow, While, under normal conditions, grasses are able to pro- 
duce roots only from the nodes, these galls are clothed with a 
thick matting of roots produced from the pericambial layer of the 
internodes. When first found these roots differ in no respect 
from ordinary underground roots, being provided with a root- 
cap, and a central vascular cylinder with a few pitted vessels, but 
with no root-hairs. In the course of development they assume 
more and more the character of aerial roots, and lose their 
root-cap. 
* — Count G. de Saporta enters into an elaborate reply, in the 
Bulletin of the Geological Society of France (x11, p. 179), to the 
theory of Nathorst that the supposed organic remains of a very 
early geological period are in reality the petrified impressions of 
the footprints of animals. He maintains that a minute examina- 
tion of their structure entirely contradicts this view, and that even 
those about which Nathorst expresses the greatest doubt may be 
petrifactions of algz in half-relief. 
— Dr. F. W. Goding announces for early publication Lives 
of eminent economic entomologists of North America, a wor! 
to consist of about 150 parts, with plates. Price, $2.00, $2.50 and 
$3.00. ubscriptions to be sent to the author at Ancona, 
Livingston county, Illinois. 
— Mr. E. T. Cresson, of Philadelphia, the well-known hymen- 
opterist, after a long interval of forced cessation from scientific 
work, has returned to the study of the Hymenoptera, and is pre- 
paring a synopsis of the whole order which he intends shortly to 
publish. 
— Dr. P. R. Uher has prepared a catalogue of the Hemiptera 
Heteroptera of North America. It is published by the Brooklyn 
Entomological Society, and can be had at the price of 50 cents 
of Mr. John B. Smith, U. S. National Museum, Washington, 
D 3 
ke . 
