

IQI7] 



KENOYER— NECTAR SECRETION 



259 



light. Haupt finds that in most extrafloral nectaries even dis- 

 turbances in photosynthesis by darkness show their influence on 

 secretion only very slowly. Light in Vicia doubtless increases the 

 permeability of the protoplast, as Lepeschkin (15) has found that 

 it does in the pulvini of Leguminosae in general. 



Schimper (23) found that extrafloral nectaries on the leaves of 

 Cassia neglecta cease their activity in a few days when the plant is 

 kept in darkness or in an atmosphere deprived of carbon dioxide, 

 but that secretion continues when the leaf is in the light and only 

 the nectaries are darkened. 



I experimented upon both the floral and the extrafloral nectaries 

 of Impatiens Sultani, and it seems clear that the withdrawal of 

 light makes its influence fairly rapidly and very decidedly felt. 

 Table IV gives a typical study of floral nectaries, the measurements 

 being millimeters in length of the part of the spur which contains 

 nectar. The table includes average increases over last measure- 

 ment of the spur in those flowers which were open when the last 

 record w r as taken, and the average measurement for those flowers 

 which have opened since the last record. One plant was covered 

 by a bell jar, the other was covered by an opaque jar of about the 

 same size. 



TABLE IV 



Days 



Light 



Dark 



Gains 



2 



3 



4 

 6 



7 



8 



9 

 10 



4 



4 



2 



3 



5 

 4 



3 

 3 



4 



8 



o 



1 



3 

 2 



New flowers 



Gains 



New flowers 



21.6 

 22.0 

 23.0 

 29.0 

 20.0 

 21.7 

 19.0 

 22.0 





time 



1.2 



16. 1 



I . t 



13.6 



I I 



15-7 



— 1.2 



17 -3 



O. I 



16.0 



o-5 



14.0 



-0.4 



130 



-0.5 



0.0 



n on an 



etiolated appear 



/elooins:. 



Secretion fron 



ance and new flowers were scarcely developing. 



extrafloral nectaries had practically stopped after 3 days in the dark. 



Half the leaves of a plant were covered with black tissue paper 



means 



