DEPARTMENT OF BOTANICAL RESEARCH. 61 



action on the rate of respiration. No satisfactory explanation of these 

 results has thus far been obtained. Experunents conducted to reveal 

 a possible isomerizing action of the amino-acids on these various sugars 

 in vitro as well as in the leaf yielded only negative results. Efforts 

 are now being directed to determine the enzymatic relations in the 

 leaves and how these are influenced by the various nutritive condi- 

 tions. Herein special attention is given to the catalase and peroxidase 

 activities. These are of importance not only to the respiration of the 

 leaf but also to the photosynthetic activity, and it now seems highly 

 probable that herein lies the link which so intimately binds these two 

 processes. 



The analytical determination of amino-acids in plants ranging from 

 germinating seeds to mature plants has been continued in connection 

 with their respiratory activity and carbohydrate content. It has 

 become evident that in these relationships the chlorophyllous leaves 

 are quite differentiated from other parts of the plant. These inves- 

 tigations are now being extended to include a study of the circum- 

 stances which make for the synthesis of proteins and their break- 

 down into simpler compounds. 



The Internal Factor in Photosynthesis, hy H. A. Spoehr. 



The only reliable methods which have thus far been developed for 

 the study of photosynthesis in land plants are those based upon gas 

 analysis. In attempting to improve further the apparatus used in 

 these studies, various other methods were tried out which made 

 use of various different principles other than the differential determi- 

 nation of the carbon dioxid in the air-stream passing over the illumi- 

 nated leaf. None of these proved as accurate nor as convenient as the 

 latter. Methods were therefore devised which made use of the elec- 

 trolytic determination of carbon dioxid by means of absorption in 

 solutions of barium hydroxide, as had been done in the investigations 

 on respiration. Suitable absorption tubes and sedimentation vessels 

 of glass were constructed, which permit of complete absorption of the 

 carbon dioxid. By means of a special electrolytic cell of high resis- 

 tance the electrical conductivity of the barium-hydroxide solutions 

 can be measured with both great accuracj^ and rapidity. 



Since these investigations were started a mass of evidence has accu- 

 mulated which supports the dictum that an essential role in the photo- 

 synthetic process must be ascribed to the protoplasmic activity of the 

 colorless components of the chloroplasts. The existence of an essential 

 internal factor can be concluded not only from the failure of all 

 attempts v/hich have been made to reproduce photosjmthesis outside 

 of the living cell but also from direct experunents with living leaves. 

 That this factor is not to be sought in the chlorophyll components or in 

 such physical conditions as the degree of dispersion of the chlorophyll 



