WEATHER AND CHANGE IN WEIGHT OP BEE COLONY 37 



He concludes that the influence of light on the secretions of the nec- 

 taries is of an indirect nature, except in the case of Vicia and some 

 species of Euphorbia, these exceptions being noted by Haupt (17). 

 As a matter of fact, Ono concludes that all external factors are of 

 slight value in comparison with the inner conditions of the nectaries. 

 Secretion, he thinks, may occur by mere chance; and the factors 

 which are favorable to the life and growth of the plant at the same 

 time promote the secretion of nectar. 



Haupt (17) found that for certain plants, e. g., Euphorbia and 

 Vicia, the secretion of nectar is profoundly influenced by light, 

 especially by the red and yellow rays of the sun's spectrum. The 

 secretion of nectar occurs only in light, and in darkness or in blue 

 light nectaries already containing sugar resorb this substance. 



Gardiner (12), in commenting on the discoveries of Wilson (33) 

 regarding nectar secretion, says, "I am led to think that this goes far 

 to explain both his own and Darwin's (6, p. IfiS) observations, that 

 the exudation of nectar takes place more rapidly in sunlight, for 

 according to my own observations as regards waterglands and the 

 like it does not seem probable that the power of secretion as such is 

 accelerated by light." However, Wilson (33) does not lay much 

 stress on the effect of light upon secretion, as Gardiner would have 

 one believe, for in Wilson's conclusions he states that many plants 

 secrete as well in the light as in darkness, while others require either 

 direct sunlight or strong diffused light for secretion. Harrault (14) 

 observed that some plants can yield certain quantities of nectar 

 under weak solar rays but that most plants do not yield nectar even 

 in slight shade. In discussing the influence of external factors on 

 plant transpiration, Livingston, in his revision of Palladin's work (27, 

 p. 138), says that light is undoubtedly the most important. 



In the present investigation the total hours of sunshine seem to 

 have a somewhat greater effect upon net gain during the spring 

 period than does solar radiation. The coefficient of correlation of 

 the former with net gain is .6124 ±.0683, while for the latter with 

 net gain it is .5525 ± .0760. In the attainment of the flowering stage 

 of plants, Garner and Allard (13) found that length of day is much 

 more important than the total amount of solar radiation received 

 by the plant. This discovery is interesting in view of the fact that 

 the secretion of nectar accompanies the attainment of the flowering 

 stage for practically all of the important nectar-producing plants. 



These writers state that — 



Except under such extreme ranges as would be totally destructive or at least 

 highly injurious to the general well-being of the plant, the result of differences in 

 temperature, water supply, and light intensity, so far as concerns the sexual re- 

 production, appears to be, at most, merely an accelerating or retarding effect, as 

 the case may be, while the seasonal length of day may induce definite expression, 

 initiating the reproductive processes or inhibiting them, depending on whether 

 this length of day happens to be favorable or unfavorable to the particular 

 species. 



Further investigation along these lines may result in throwing more 

 light on the effect of weather factors on bee behavior, and on plant 

 behavior in so far as the secretion of nectar is concerned. A corre- 

 lation of length of day with nectar secretion of various plants may 

 likewise help to clear up the many differences in plant behavior which 

 beekeepers attribute to differences of locality. 



