250 BOTAXICAL GAZETTE [april 



evidence that the first of Pfeffer's theories is the correct one for 

 the excretion of water drops. Wilson- (29) gives evidence in sup- 

 port of Pfeffer's third theory, showing that the thorough washing 

 of a nectary stops the secretion if the nectary is past the stage of 

 metamorphosis of the cell wall, but that secretion is resumed on 

 the addition of sugar to the surface of the nectary. The validity of 

 his results is called in question by Lepeschkin (14) and Busgen (5). 

 Haupt (10) in a study of extrafloral nectaries finds that some 

 nectaries become inactive after washing, while others, as those of 

 the leaves of Impatiens parviflora, continue excretion of water but 

 not sugar, thus becoming equivalent to hydathodes. Livingston 

 (16) likens nectar secretion to guttation, accounting for the latter 

 by a decrease in the permeability of the plasma membrane induced 

 by an increased turgidity, and for the former by a hypothetical 

 rapid increase in the solute content and thereby of the osmotic 

 pressure in the cell, a change which induces a like decrease in the 

 permeability of the membrane. 



Comparatively little work has been done on the chemistry of 



nectar. Wilson (28), Von Planta (27), and Bonnier (i) have 

 analyzed a few kinds of nectar, finding that in some cases it con- 

 tains no sucrose, while in others it is almost wholly this kind of 

 sugar. In some cases fructose and in others glucose is the domi- 

 nating reducing sugar. The sucrose of nectar is almost wholly 

 digested in honey, Browne (4) finding as the average composition 

 of 138 honey samples from widely separated localities 38.65 per 

 cent fructose, 34.48 per cent glucose, and 1. 76 per cent sucrose. 



Investigation 



METHODS 



m 



means of a graduated capillary pipette, or weighed after absorption 

 on strips of filter paper which had previously been weighed in small 

 vials. Many of the most important honey plants secrete such 

 small amounts of nectar to the individual flower that neither of 



methods 



determined 



amount of sug 













