SECRETARY’S REPORT 125 
the division, has as far as possible arranged to bring current projects 
to satisfactory completion and to undertake no new projects except 
those of short duration. 
Dr. Weintraub, after his transfer to a National Defense agency, 
continued periodic visits to the division to complete certain phases 
of his work. In these visits Mr. Price found his advice and aid of 
much value in rounding out the current experimental work. The fol- 
lowing summarizes the work accomplished : 
Several years ago, Dr. McAlister developed in the division an in- 
strument for measuring accurately and quickly by spectroscopic 
means the carbon dioxide content of a volume of gas. Dr. Johnston 
later made certain modifications and carefully tested the instrument. 
Dr. Weintraub and Mr. Price subsequently used it in a study of the 
effect of plant growth regulators on the respiration of potato tubers. 
After the construction of a larger respiration chamber, a similar study 
was started using broad-leaf plants. This project was nearly com- 
pleted at the close of the year. 
Two new thermostats, installed early in the year, aided greatly in 
the control of environmental factors in germination studies using 
lettuce seeds. The effects of temperature, light, composition of at- 
mosphere, and composition of substrate have been studied individually 
and in combination. Two phases of this study are completed and a 
third nearly completed. 
Considerable progress was made in studies of the developmental 
physiology of grass seedlings. Growth curves for both mesocotyls 
and coleoptiles of plants grown under various combinations of con- 
trolled environmental conditions have been obtained. Plants grown 
in various salt solutions have yielded information on cation and anion 
effects. Salts show a retarding effect during initial germination 
which is then followed by a period of extended growth beyond that 
of plants grown in the absence of salts. The retardation and extended 
growth periods are proportional, within limits, to the concentration 
of the salt used. Several papers on these developmental physiology 
studies are in preparation. 
The histological study of the mesocotyl, which was undertaken to 
explain the gross morphology effects of various environmental con- 
ditions, was continued for only part of the year. Being a long-range 
project, it was abandoned to permit the completion of other projects 
that were further advanced. However, before this work was stopped 
the cellular development of mesocotyls of etiolated corn seedlings had 
been charted. 
A report is in preparation on the study of the effects of various 
fungicides on the germination and development of grass seedlings. 
Experimentation for this problem has been completed. 
