1917] KEXOYER— NECTAR SECRETION 255 



between maximum and minimum daily temperatures which pre- 

 vails at high altitudes and latitudes, or to the greater range in the 

 humidity of the air. 



Phillips (21) observes that alfalfa in general is valuable as a 

 honey plant in the Great Plains region of the west and not in the 

 eastern states; that buckwheat is of more value in New York, 

 Pennsylvania, and Michigan, than in Indiana and Illinois; and that 

 white clover is of greater importance in the north than in the south. 

 Basswood is said to secrete better in the more northerly portions 

 of its range. It seemed desirable, therefore, to investigate the 

 hypothesis of Bonnier. 



As I have show r n (12), the study of a 30-year weight record of 

 a hive at Clarinda, Iowa, lends strong support to this assumption. 

 Thirty-eight periods of continual and fairly rapid gain in weight 

 were selected, and the days of each divided about equally betw r een 

 days of high gain and days of low gain. In 32 cases the average 

 diurnal temperature range for the days of high gain was greater 

 than that for the days of low gain. In all of the 6 exceptional 

 cases the difference between the average was small. Sladen (25) 

 states that the heaviest single day's increase in hive weight noted 

 for two seasons in England in a record kept by Ede w r as on a day 

 that began with a heavy early morning frost, the honey coming 

 from the heather (Calluna vulgaris). 



Table III represents the amount of reducing sugar in mg. which 

 the author found after keeping the plants or flowering branches for 

 a time in the incubators. 



In field conditions it can readily be shown that lower tempera- 

 tures increase the sugar content in dandelion and the clovers. 



How does high temperature influence secretion ? Van Ryssel- 

 berghe (26) determined that with increase in temperature the 

 permeability of the protoplast to water and solutes rapidly increases, 

 that of Tradescantia epidermal cells for water being 8 times as great 

 at 30 as at o°, and that for solutes seeming to follow the same pro- 

 • portional rule. To demonstrate whether this holds for nectary 

 cells, I determined the lowest sucrose concentration necessary to 

 plasmolyze the multicellular secreting hairs which cover the nectary 

 of Abutilon. After 4 days at io° a 0.6 molecular solution is 



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