

260 BOTAMCAL GAZETTE [april 



basal or nectar-secreting teeth being left uncovered. These leaves 

 secreted very little after the third day, whereas the uncovered 

 leaves of the same plant were uninterrupted in their secretion. 



Buckwheat flowers were gathered at the same time from under 

 light and dark jars, and it was found that after two days in the dark, 



although the total amount of liquid secretion was not in the least 

 diminished, the proportion of sugar began to decrease, the secre- 

 tion not tasting sweet or giving a very positive sugar test. An 

 average of 1 1 such analyses of the nectar of flowers that had been 

 covered for 2-8 days gives per 10 blossoms 1 . 20 mg. invert sugar 

 in the light, and 0.41 mg. in the dark. Sugar contained in the 

 flowers does not differ greatly, however, in the two cases, there 

 being o.79mg. to 10 flowers from the light and o.73mg. to 10 

 flowers from the dark. Plants which had been left in the dark for 



time continued to secrete less than normal quantities of 



some 



more after the removal 







diminution 



a number of plants. 



;h 



mi 



from 



remov 



from 



checks. Seven of the above pairs of cases give for the entire 



mg 



and 0.92 mg. from the check. 



The same result may be gained by covering all the leaves of the 

 plant with black tissue paper, and comparing the nectar with that 

 of normal plants. Here we find as an average of 6 analyses of 10 

 flowers o. 2$ and o. 69 mg. invert sugar respectively in the nectar; 

 0.83 and 1.40 in the whole flowers. After 4 days in the dark 

 there is approximately one-fourth as much sugar secreted per 

 flower. 



When the flowers only are covered from the light, they secrete 

 fully as much sugar as those not covered ; so the extrusion of sugar 

 is clearly dependent upon the food reserves of the plant. 



relation to exist in the Canna blossom. Dark- 



same 





materially diminished 



while darkening the flower cluster alone had no influence upon it 



