446 University of California Publications in Botany [Vol. 5 



ether effects are dependent upon its concentration. Normal destruc- 

 tion of proteins in the germination of Pisuni and Lupinus was retarded 

 by doses up to approximately 0.01% by volume, but the process was 

 accelerated in strong doses. Also Johannsen (1896) found that certain 

 concentrations of ether and chloroform caused an increase in soluble 

 sugars and in the decomposition of proteins in bulbs of Crocus and 

 seeds of barley and pea, while very weak doses gave the reverse effects, 

 i.e., favored starch and protein synthesis. 



The definite response of variety "Washington navel as compared 

 with the other Citrus material is quite in keeping with the normal 

 reaction of these plants whereby under certain conditions of tempera- 

 ture and humidity they drop their immature fruits, while correspond- 

 ing environmental conditions have a much less corresponding effect 

 upon other species of Citrus. In this connection attention must be 

 called to the differences in the average reaction times for the controls, 

 in that flowers of variety '^N'ashington navel fall in respectively two- 

 thirds and one-half the time that is necessary for flower-fall in the 

 other two forms. This gradient is rather remarkable from a number 

 of points of view and our results should be confirmed and extended 

 and similar determinations made for other Citrus varieties. 



The experiments in which tlie pure constituents of illuminating gas 

 were employed were marred by our inability to maintain constant 

 temperatures during their course. The influence of variations in 

 atmospheric temperature in such abscission experiments was apparent 

 from the start and some preliminary efforts were made to determine 

 it. One of a series of the moist chambers, noted above as employed for 

 the controls in the experiments with Citrus, was placed in an incubator 

 and run for some time at approximately ten degrees above room 

 temperature. Foliar abscission under such conditions appeared at the 

 end of thirty hours, while the control run at room temperature showed 

 the first leaf-fall at fifty-six hours. The variation in the reaction time 

 of the controls given in table 2 is rather great, but the results of 

 experiments 3, 4, and 5 in this table show that this variation does not 

 need to be given too much weight in connection with the effects of the 

 various gases in causing abscission. This variation, however, appears 

 to be indicative of changes and instability in the general physiological 

 condition of the plants under investigation. The experiments listed 

 in table 2 were carried on at practically the end of the normal growing 

 period of the plants used and ordinary experience and the results of 

 other workers Avould suggest that this fact might influence to some 

 extent reactions to specific stimuli (cf. Lloyd, loc. cit., p. 69). 



