1917] 



KEN OYER— NECTAR SECRETION 



257 



1 



of nectar is a balance between two factors, namely, the accumula- 

 tion of sugar in and near the flower under the influence of low 

 temperature, and increasing permeability of the plasma membrane 

 under the influence of high temperature. The position of the 

 optimum, then, might be represented somewhat as follows: 



Graph of sugar accumulation 



Graph of permeability of 

 protoplast to sugar 



Optimum secretion temperature 



Temperature o 



10 



20 



30 



The two graphs are limiting factors to nectar secretion, and the 

 intersection, that is, the point where the effective limit stands 

 highest, is the optimum secretion temperature. If the fact dis- 

 covered by Eckerson (7) for root cells, that above a certain point 

 (25-35°) the permeability again decreases, applies also to nectary 

 cells, the situation may be somewhat complicated thereby. 



Better than any uniform temperature for secretion is a change 

 from a lower to a higher temperature, as table III indicates. The 

 influence of such a change might be graphically indicated by folding 

 the above diagram so that two temperatures, say io° and 30° are 

 brought together. Both limiting factors are raised; the sugar 

 which has accumulated at the lower temperature is secreted at the 



higher. 



ATMOSPHERIC PRESSURES 



In the study previously cited (12), I have shown that of 18 

 periods of continual honey production, 16 have a lower barometric 

 pressure on the days of heavier yield than on the days of lighter 

 yield, the two exceptional cases having very slight differences. The 

 increased secretion already credited to high altitudes might be 





