14 ART. 3. K. ONO. 



are of slight value comj^ared with the inner conditions of the nectary. 

 When the plant is growing vigorously and its nectaries are fully de- 

 veloped, the secretion may occur by mere chance. Generally speak- 

 ing, the external conditions favourable to the life and growth of the 

 plant itself, promote at the same time the secretion of the nectar. 



The mechanism of the secretion of the nectar has recently 

 been studied by Haupt,^^ who found that light, heat and moisture 

 are the conditions which principally modify the secretion. I have 

 also made some experiments on these conditions, the results of 

 which may briefly be described as follows. 

 a. Influence of moisture. 



Moisture is one of the conditions most favourable to the 

 secretion of the nectar, and its influence seems to be more or less 

 direct. Dry atmosphere is in all cases unfavourable to the secretion. 



In open air, nectaries are found to secrete more nectar in 

 warm damp weather than on dry windy days. When a plant, 

 the nectaries of which are inactive in the open air, is put under 

 a moist bell-jar, the secretion often takes place. For this expe- 

 riment I took the following plants : Prunus Laurocerasus ; P. 

 yedoensis ; P. persica ; Idesia polycarpa ; Mallotus japonieus ; 

 Alewrites cordatus ; Dlospyros Lotus ; D. morissiana ; Viburnum 

 Opulus ; V. japonicum ; Diervilla grandiflora ; D. ßoribunda ; 

 Ligustrum japonicum ; L. lucidum ; Polygonum cuspidatum ; 

 P. sachaliyiense ; Sterculia 2)latanifolia ; Callicarpa japonica. 



Cut twigs of Prunus Laurocerasus, put in a water bottle and 

 held under a bell-jar in moist air, continued to secrete the nectar 

 during the three weeks — from April 21st to May 10th, the washing 

 of the nectary being repeated daily. Neither the quantity of the 

 nectar, nor the sugar in it, decreased throughout the experiment. 



1) Ilaupt, 1. c 



