470 BOTANICAL GAZETTE [JUNE 
When a plant is rotated on an equally rotating horizontal clinostat, a convex 
curving always occurs regardless of the orientation of the plane of the blade 
with the axis; this is an epinastic movement. When the plane of the blade is 
vertical and the midrib horizontal, the leaf is said to be in a flank position; 
it is evident that there are two flank positions. If a leaf is left in a flank posi- 
tion, the petiole shows both a torsion and a convex bending which finally give 
the blade the normal horizontal position. By use of an intermittent clinostat 
which gives repeated 5-15 minute exposures in one flank position followed by 
equal exposures in the other, all torsion is avoided, but convex curving takes 
place. The successive flank exposures equalize the effect of gravity and allow 
epinasty to express itself. By use of the intermittent clinostat, equal exposures 
between —45° and the two flank positions were given. In this case concave 
bending occurred, showing that the geotropic stimulus entirely overcame the 
equally rotating clinostat that concave bending will appear? This is easily 
accomplished by the use of the oblique clinostat and the combined angles that 
are possible onit. The great possibility of combinations of angles of geotropic 
exposure due to variation in obliquity of the clinostat axis and the obliquity 
of the organ axis with the clinostat axis has been emphasized by FITTING. 
This work is the natural outcome of the improved methods that FITTING 
has given for dealing with problems in geotropism.—WILLIAM CROCKER. 
Photosynthesis.—Scuryver’ believes that he has thrown some light on 
the mechanism of carbon fixation in green plants. He first describes a modi- 
fication of Rimini’s test for formaldehyde. By the test as modified, 1 p-P-™- 
formaldehyde gave the reaction, and by proper modification, both free and 
combined formaldehyde can be detected. Rather accurate quantitative 
estimates can be made in concentrations varying from 1 part in 100,000 [0 
T part in 1,000,000. Films of chlorophyll were formed on glass plates by 
evaporation of ether solutions. Such plates, exposed to light in the presence 
of moist CO,, showed a marked formaldehyde test; those similarly ¢ 
and those in darkness none. The 
formed from CO, produced by the chlorophylt film. He believes the formal- 
dehyde formed makes a rather stable compound with chlorophyll, much “9 at 
does with amino-containing compounds. He considers the reaction reversible, 
and represents it as follows: Chloro#y+HCHOs Chloro— CH:+H.0- 
The removal of CH,O in sugar formation will cause the reaction to move aie 
Proc. Roy. Soc. London B 82: 226-232. 1910. 
