116 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
mental factors can be interpreted as resulting from an influence upon 
the water uptake. 
b. Growth of coleoptile—A marked effect of temperature upon 
the growth inhibition of the oats coleoptile by light has been observed. 
Below 25° C. the inhibition is independent of temperature; between 
25° and 30° the inhibition effect becomes smaller as the temperature 
increases; above 30° there is no inhibition and possibly a slight stimu- 
lation by light. These statements apply, of course, only to the specific 
conditions of intensity and wave length which have been studied. An 
improved thermostat is being constructed so that the experiments can 
be extended with greater precision. b 
c. Root.—A very interesting effect of light upon root growth has 
been noted. Roots which are caused, by mechanical restraint, to 
grow in a horizontal direction elongate at their normal rate in dark- 
ness, but are greatly inhibited by light. In addition to the interest 
in the mechanism by which this result might be caused, it is noted 
that red light is effective, indicating the presence of a pigment which 
absorbs these wave lengths. 
d. Cells.—Histological studies of the mesocotyl have been initiated 
in order to correlate the gross effects with the cellular development 
of this organ. 
e. Technique—In cultures of seedlings at high humidity and tem- 
perature a complication is introduced by the abundant development 
of molds. Considerable time has been devoted to devising techniques 
for inhibiting mold growth without influencing the development of 
the higher plants. As the result of tests with about 200 fungicidal 
chemicals a few have been found which appear promising. Steriliza- 
tion by ultraviolet irradiation also has been found effective. 
PERSON NEL 
On March 9, 1946, the Observatory lost by death Lyman A. Fillmen, 
instrument maker for the past 15 years. His place was filled on Apri! 
8, 1946, by Darnel G. Talbert. 
A. G. Froiland, on military furlough since July 8, 1943, returned 
as astrophysical aid November 16, 1945. In February 1946 he was 
promoted to associate astrophysicist and transferred to Montezuma, 
Chile, where he assumed charge of the Montezuma station, replacing 
F. A. Greeley. Mr. Greeley returned to Washington in May, and at 
the close of the fiscal year was enjoying a well-earned vacation. He 
and Mrs. Greeley had for 3 years carried on the arduous work of the 
Chilean station unaided. 
In September 1945 A. F. Moore, director of the Tyrone station, ex- 
changed stations with S. C. Warner, director of the Table Mountain 
