The Cause of the Excretion of Water on the Surface of Neclaries. 5 



The nectaries on which the excretion of fluid has been stopped hy 

 washing may reniain under a bell-jar in the niost favorable conditions for 

 excretion, but will continue dry until the flowers wither. 



Having treated a düster to washing until there is no further excretion, 

 let US on a part of the nectaries place small partieles of moistened sugar, on 

 others minute drops of sugar-sirup, and still others we will leave unpro- 

 vided wilh either. We will so arrange it that in some flowers there are 

 nectaries provided with sugar or sirup and others with nothing on their 

 surfaces. Retaining these flowers under a bell-jar and observing what 

 happens we shall soon see the fluid on the surface ofthose nectaries provided 

 with sugar or sirup slowly returning. In the course of two or three hours 

 these nectaries will have their natura! appearance, each being provided 

 with its large drop of clear fluid hanging out from the concave nectary. 

 But the nectaries in the same flowers, where sugar or sirup was not ap- 

 plied, remain dry and unchanged. 



As a still further test a few of the nectaries on which the excretion 

 has been induced with sugar may be again washed. Once or twice suffices 

 to stop all excretion. 



When these nectaries secrete no looger, i. e. after the washing, we may 

 once raore add sugar or sirup, which again as readily as at first, induces the 

 excretion. which continues as tbough not before interrupfed. By these ex- 

 periments it will be seen that the flow of nectar can be whoUy controlled 

 by externa} treatment. 



The relation existing here between the induced water current on the 

 animal membrane or leaves, and the excretion of the nectaries of Fritillaria 

 imperialis will readily be observed. In both cases the current from the 

 interior to the exterior is the result of Osmose, caused by the existence of 

 a Solution on the surface of the membrane or nectary of a different quality 

 from that existing in the interior. 



How this fluid takes its place on the surface of the nectary is not 

 wholly clear in all cases. 



On many nectaries the upper layers of the walls of the epidermis-cells 

 become disorganized; a fluid resulting from this metamorphosis raises, and 

 finally bursts the overlying cuticula, and gives the first Impetus through 

 osmotic action to the current which flows from the parenchyma of the 

 nectary to its surface. 



On the glandulär hairs of Primula sinensis i), Cistus creticus, Pogoste- 

 mon Patschouli and many others, we have analogous examples of a fluid 

 produced between the cell-walls and the cuticula. The same phenomenon 

 has been observed in the excretion of gums, resins and viscid substances 

 which are often found on the surface of buds, serving for their winter pro- 



1) De Bary, Vergleichende Anatomie, 1877. p. 95. 



