1917] 



KENOYER— NECTAR SECRETION 



2O3 



arrest in the development of the organ. In the case of floral nec- 

 taries, therefore, it is most pronounced after the ovary has attained 

 maximum development and before the fruit has commenced to 

 develop. He finds a maximum proportion of sucrose in the floral 



time 



Chemical 



analyses of the floral tissues show that the climax of sugar accumu- 

 lation is about the time of the dehiscence of the stamens, and that 

 as the flower withers there is a very rapid decrease in the amount 

 of sugar. Table VII gives some examples from my work, the 

 tissues having been extracted and purified. 



TABLE VII 



Species 



Buds 



Invert 

 sugar 



Sucrose 



Medicago sativa per gm . . . 



Melilotus alba per gm 



Melilotus officinalis per gm. 

 Trifolium repens per gm . . . 

 Trifolium hybridum per gm. 

 Taraxacum officinale 



gm 



per 



Impatiens Sultani per 100 

 flowers 



Lilium speciosum rubrum 

 per flower 



Lilium longiflorumf younger 

 per flower \older . . . 



32 

 22 



16 



8 



13 



5 



2 



o 



1 

 8* 



■ 



Mature flowers 



Invert 

 sugar 



17.8 



2.8 



2.6 

 O.O 

 O. I 



47-5 



"9-5 

 51.4 



95 9 



0.0 



26.7 

 14.9 

 21.3 



654 



3ii 

 28.8 



8.3 

 8.6* 



Sucrose 



Declining flowers 



Invert 



sugar 





27.2 

 248.4 



179 3 

 95-2 



0.0 



Trace 

 0.0 

 1.8 



0.0 



10.9 

 ii-3 



26. 1 



7-5 



190.0 



76.0 

 22. 2 



Sucrose 



O.O 



OO 



48.9 



I.O 

 O.O 



* Including sucrose. 



most 



form oj 

 begins. 



mmary 



1. By increasing humidity the secretion from nectaries of water 



but not that of sugar is increased. 



o — — — 



. Excessive water supply lessens the sugar surplus in the parts 

 of the flower. 



3. Dilution and washing by rain cause much of the sugar of 

 nectar to be lost. 



4- Rate of secretion for both sugar and water increases with 



temperature up to a certain optimum. 



