222 BOTANICAL GAZETTE | SEPTEMBER 
unable to endure continued existence in an atmosphere free from 
CO,. The slowly developing leaves of many woody perennials 
develop normally and endure long continued existence under 
the above circumstances. This varying reaction of leaves is 
dependent upon a series of conditions which may be included 
under the title of ‘availability of the food supply.” The death 
of a leaf in an atmosphere free from CO, is due to insufficient 
nutrition, and not to the pathological effects of disintegrated 
chlorophyll. 
R. N. Day: The forces determining the positions of leaves.— 
Epinasty and hyponasty are inherent properties of leaves, whose 
reactions may be suppressed but not altered by external condi- 
tions. Dorsiventral leaves are diaheliotropic, diageotropic, of 
apogeotropic, epinastic or hyponastic. The predominating 
force in every instance is the heliotropic tendency, which sup- 
pressed other reactions. The position of the leaf isa physiolog- 
ical, not a mechanical, resultant, and cannot be expressed by the 
parallelogram of forces as proposed by Krabbe in 1889. 
N. L. Britron: On Crategus coccinea and its segregates.— 
The necessity of observing living forms in various stages of 
growth was pointed out. Typical C. coccinea is known by - 
cordate leaves, moderately glandular inflorescence, etc. Occur- 
_ ting with it, and lost sight of, has been C. rotundifolia, with 
smaller oval or oblong leaves narrowed at base, larger flowers, 
a densely glandular inflorescence, and a different time of bloom- 
ing. Other segregates are C. flabellata, a northeastern species, 
with leaves narrowed at base and more incised; C. macracantha, 
the species with smallest fruit; and C. mollis. 
i M. UnpvERwWoop and F. S. EarLeE: The distribution of the 
Species of Gymnosporangium in the south—This paper appeat> in 
full in this number of the BoranicaL GAZETTE. 
L. H. Bairey: Morphology of the Canna flower— The author 
called attention to the prevailing asymmetry in the Scitamine®, 
