STUDIES ON SO.AIE EXTKANUPTIAL NECTARIES. 15 



Only towards the end of the fourth week, did the leaves become 

 yellowish, and the nectar decrease in quantity. Finally the 

 leaves withered and fell. 



During the experiment, when I took the plant out of the moist 

 bell-jar and put it in dry atmosphere, I noticed that the secretion 

 stopped at once, but began again on being replaced in moist air. 



Under the same conditions. Primus yedoensis and P. persica 

 were observed to secrete the nectar very copiously four times ; 

 and Viburnum japonicum five times. Among the nectaries of 

 the first type, Polygonum sachalinense, P. cuspidatum, Ligustrum 

 medium and L. lucidum did not secrete at all, when once washed 

 out, though I treated them carefully and kept them under favour- 

 able conditions. Vicia faha, V sativa and Diervilla grandiflora 

 secreted the nectar only twice under the same treatment. 



Vicia faha, which is active in secretion under normal condi- 

 tions, did not secrete, when put in a small dry chamber, the air 

 in which was kept dry by means of calcium chloride. With 

 Viburnum japonicum, V. optdus and Idesia polycarpa, I obtained 

 .exactly the same result. 



In general the nectaries of the second type are more vigorous 



in the secretion of nectar than those of the first type. This 



difference in secretion, between the nectaries of the first type and 



those of the second, chiefly depends upon their different structures. 



b. Influence of temperature. 



The influence of temperature on the secretion of the nectar, 

 within the range of 15°-2o° C. is not remarkable and seems to 

 have merely an indirect effect, in so far as it affects the plant 

 itself. In estimating the influence of temperature, it is necessary 

 to eliminate the influence of humidity, which has a much greater 

 influence on the secretion. 



