1917] KENOYER— NECTAR SECRETION 253 



10 blossoms in the humid and o. 98 mg. per 10 blossoms in the dry. 

 More sugar accumulates in a dry atmosphere and practically the 

 same amount is excreted. 



The accumulation of sugar under low moisture conditions is in 

 line with the discovery by Lundegardh (17) that increase of mois- 

 ture favors the accumulation of starch; decrease of moisture favors 

 its digestion. 



Six plants of Impatiens sultana in saturated air accumulate in 

 a day 3 . 26 mg. sugar each from the extrafloral nectaries (the basal 

 teeth of the leaves), while 6 plants in greenhouse air accumulate 

 5.42 mg. sugar each. The excess of the latter is very likely due 

 in part to the running away of drops under the humid conditions. 

 The nectar averages 23.4 per cent sugar in the former and 45.3 

 per cent in the latter. 



RAINFALL 



The author has shown in a statistical study (12) that heavy 

 rainfall just before the secreting season is advantageous, as it gives 

 the plants greater vigor. But during the season of greatest secre- 

 tion good years are somewhat drier than poor. Also a rainy day 

 shows a lighter honey yield than a day before or after the rain. 

 The deterrent effect of the rain on the honey flow is twofold: it 

 hinders the activities of bees and it washes away the nectar. To 

 illustrate the latter point, in 191 5 on the morning following a day 

 of continual rainfall, red clover corollas w r ere found to contain 



0.02 mg. sugar per gm 



contained 



3 . 8 mg., a day later o. 6 mg., and 2 days later 4.4 mg. Buckwheat 

 blossoms w r ere subjected to an experiment to determine the extent 

 to which rains wash away the nectar. Flowers subjected before 

 gathering to a spray for 20 minutes, 15 mm. of water falling, were 

 found to contain o.i2mg. per 10 as against 1 . 28 mg. per 10 of 

 untreated flowers. A 30-minute rain of 35 mm. reduced the nectar 

 of red clover blossoms from 0.48 to o. 19 mg. per 10, and that of 

 wniic clover blossoms from o. 27 to 0.07 mg. per 10. 



TEMPERATURE 



Wilson (29) states that temperature has not a marked effect 

 upon the rate of secretion of nectaries that have commenced 



