108 CARNEGIE INSTITUTION OF WASHINGTON. 



that these physiological differences can be ultimately reduced to 

 physico-chemical terms. One is led, therefore, to expect an asso- 

 ciation between the structure of organs and the physico-chemical 

 properties of their cellular juices. These problems, which have up 

 to now been treated at this Station only from the physiological stand- 

 point, are now being studied from the chemical side in collaboration 

 with Dr. Gortner. It is as yet too early to justify any generaliza- 

 tions, but the results are most encouraging. 



Studies of osmotic pressure, electrical conductivity, and mean 

 molecular weight in the juices of normal and structurally aberrant 

 Passiflora fruits seem to show conclusively that there the distin- 

 guishing morphological features are associated with differences in 

 the physico-chemical properties of the cell-sap. Thus, the juice of 

 abnormal fruits has a higher osmotic pressure than that of normals; 

 and the average molecular weight of the substances in solution in the 

 plant-sap is, apparently, lower in the abnormal fruits. This study 

 has an especial value as a first step in the analysis of the factors 

 involved in morphological characters of the fruit. 



Dr. Harris and Dr. Gortner also made a joint study of the records 

 furnished by various experiment stations as to the relation of weight 

 of the sugar beet and the composition of its juice. They find that 

 as the weight of the sugar beet increases the total solids, sucrose, 

 and percentage purity (^. e., the ratio of sucrose to 100 parts of total 

 solids) fall rapidly. 



Inhibition of Pigmentation, by A . M. Banta and R. A . Gortner. 



Dr. Banta and Dr. Gortner have continued their experiments with 

 those phenols that inhibit the reaction tyrosinase + tyrosin in vitro 

 upon eggs and larvae of the little salamander, Spelerpes, reported in 

 the last Year Book, page 84. 



The effects of the inhibitory compounds on pigmentation are still 

 visible in the few larvae which are still alive, after having been 

 removed from the influence of the drugs for nearly a year. Dr. 

 Gortner draws the interesting conclusion that it seems probable, 

 were it possible to secure compounds which are at the same time 

 non-toxic and which inhibit the action of tyrosinase or tyrosin, that 

 permanent ''dominant whites" could be produced. Dr. Banta 

 repeated last year's experiments on Spelerpes. With the aid of last 

 year's experience the proper strength of solution for Spelerpes was 

 closely determined and correspondingly more striking results were 

 obtained. When the pigmentless larvae are placed in 0.025 per cent 

 orcinol or resorcinol three days before the pigment normally begins to 

 form, pigmentation is almost entirely inhibited for as long a time as 

 the larvae retain the inhibiting substances in their pigment-producing 

 tissues. Unfortunately the larvae can not be kept in these solutions 



