176 BOTANICAL GAZETTE [FEBRUARY 
phenomenon and the processes of transpiration and photosynthesis influenced 
by various conditions of light and temperature. These experiments seem to 
show that (1) any decided checking of photosynthesis either from light con- 
ditions or from a deficiency of carbon dioxide brings about leaf fall; (2) any 
lowering of transpiration also produces defoliation, but less rapidly than 
decreased photosynthesis; (3) variation in the intensity and quality of the 
jight has no direct specific action upon leaf fall; and (4) lower temperatures 
are efficient in causing leaf fall through decreased photosynthesis and tran- 
spiration only within limits which permit the activities involved in the develop- 
ment of the absciss layer; below these limits the leaves die, but cling rather 
persistently to the twigs. It is to be regretted that the experiments were so 
limited and hence so few data were accumulated in support of the conclusions 
reached.—Geo. D. FULLER. 
The Forest Club Annual.—Among the publications which tend to 
promote an intelligent interest in the problems of forestry this annual” from 
the University of Nebraska is worthy of something more than passing notice. 
Among the articles it contains are ‘‘Grazing investigations on our national 
forests,” by A. W. Sampson, and “Effects of forests upon run-off in the 
Rockies,” by R. D. Garver. Both present data that are important from the 
ecological as well as the economic point of view. The same may be said of 
“Notes on winter-killing of forest trees,” by C. P. HartLEy, which shows the 
need of careful investigation of the various physical factors involved before 
any adequate explanation of the action of winter conditions upon forest trees 
may be obtained. The other problems discussed include forest conditions in 
parts of Nebraska and Arkansas, forest roads, trees suitable for streets and 
parks, and some phases of lumber manufacture —Gero. D. FULLER. 
Fairy ring fungi.—These well known fungi are found by BAy.tss* to be 
parasitic upon the roots of grass. They soon kill the roots by the secretion of 
some toxic substance. The same or some other secretion is toxic to the fungi 
themselves, making them unable to grow in the same soil for three years in 
succession and hence producing the well known development of yearly widen- 
rings. Contrasted with the infected grass, that which lies immediately 
outside as well as inside the ring is stimulated into better growth by the 
greater abundance of nitrogenous food made available by the action of the. 
mycelium of the fungi in secreting proteolytic enzymes. The yearly increase 
in the radii of the rings of Marasmius oreades was found to be 6-14 inches. 
—GeE0. D. FULLER. 
Bes forest club annual, vol. 4, pp. 160. University of Nebraska, Lincoln, 
Neb. 1 
a AYLIss, Jesste S., Observations on Marasmius oreades and Clitocybe gigantea 
as parasitic fungi. Jour. Econ. Biol. 6:111-132. 1911. 
