64 re;ports on investigations and projects. 



lasa as to the function of nascent hydrogen produced by enzymases in the 

 plant-leaf. Stoklasa's experiments can only be explained to the effect that 

 the metallic hydroxides formed in his method of obtaining hydrogen play 

 the same role as the colloidal platinum in the experiments mentioned above. 

 This discovery is another step in the substantiation of the theory previously 

 put forward. Whether formic acid is an intermediate step in the photo- 

 synthesis process or whether its presence is due to subsequent oxidation of 

 formaldehyde has not been definitely established. While formaldehyde has 

 been obtained through the action of light from a great many of the acids 

 found in the leaf, conditions under which formic acid yields this reduction 

 product have not been discovered. 



A number of plant acids, under various conditions of solution, have been 

 exposed to the sunlight for an entire year. The products formed by this 

 long insolation are now being investigated. 



Thus far it has been found that acetic, glycollic, propionic, malic, tartaric, 

 and citric acids are decomposed in the light with the liberation of consider- 

 able quantities of carbon dioxide. Formaldehyde is also formed, and, in 

 the case of the higher hydroxy-acids, non-volatile substances, which reduce 

 Fehling's solution. It will be of special interest to determine what these 

 latter substances are and whether they are bodies from which sugars can be 

 formed. In general all these acids are decomposed very much more easily 

 in the form of a salt than as the free acid. It is noteworthy that formic 

 acid yields no reduction product. Indicative of the high energy content of 

 the sunlight is the fact that acetic acid, one of the most stable organic com- 

 pounds, is decomposed. 



This study has been undertaken in order to determine the function and 

 fate of the organic acids in the succulents in particular, and what role these 

 substances play in the photosynthetic process in general. 



Micro-chemical studies have been begun on isolated chloroplasts. Using 

 Helianthus and Tradescantia, methods have been found which will permit 

 the observation of the photosynthetic action of isolated chloroplasts for 

 several hours. Pure cultures of Proteus vulgaris have been used for the 

 detection of oxygen liberated by the chloroplasts. The object of the in- 

 vestigation is to establish the conditions of solution most favorable to the 

 living chloroplasts and to the photosynthetic processes, and, if possible, to 

 follow the latter micro-chemically. 



During the year daily light measurements have been made at the Desert 

 Laboratory. The catalytic action of uranium acetate on oxalic acid induced 

 by light is particularly sensitive to the violet end of the spectrum, and ac- 

 cordingly this method was employed. Observations with a Smithsonian 

 Institution pyrheliometer have been made at the same time. During the 

 month of June concomitant measurements were made at the Desert Labora- 

 tory and on Mount Lemmon, 20 miles to the northward. It was found that 

 while the differences observed with the pyrheliometer were very slight, the 



