4 W. P. Wilson. 



arabic, by means of a pipette, we shall have the same phenomenon re- 

 pealed which took place with the aniraal membrane. Upon covering these 

 leaves with a bell-jar to prevent evaporation and watching the result, we 

 shall see these small drops gradually beconie large ones, and finally in 

 cases where the leaves are much inclined, flow down the inclination and 

 drop from the surfaces. 



Here again a current of water is generaled and flows from the interior 

 to the exterior through the cell-walls. This experiment may be repeated 

 with any living plant tissue whatsoever with a similar result. 



Selecting a hollow on the surface of a potato, where there are no len- 

 ticells, and placing therein the sugar Solution we find the same quick 

 response to this osmotic action. The thick cuticula of the leaves selected, 

 and the cork layer of the potato are not sufficient to prevent the active 

 effect of this law of Osmose. In the case of the animal membrane it makes 

 no difFerence what the pressure of the water from within may be, as soon 

 as the Solution which was placed on the surface is removed by washing 

 the current ceases. The same holds true of the leaves and plant tissues of 

 every kind. 



Fritillaria imperialis. 



If we examine the flowers of Fritillaria imperialis we shall find in 

 the interior at the base of each of the perianthal divissions a large drop of 

 fluid, filling and hanging out from a rounded concavity, the nectary. lipon 

 shaking away these drops we find they soon return. 



Let US take two similar Clusters of flowers, cut from the parent plant, 

 both with actively secreting nectaries ; remove the nectar from one Cluster 

 with a pipette, being very careful not to wound the surface of the necta- 

 ries, and from the other by means of washing with a common wash-bottle, 

 drying the nectaries thoroughly with bibulous paper after the washing. 

 Observing now what happens after we have placed both Clusters under a 

 bell-jar, we shall see that the nectar appears more quickly, and accumu- 

 lates with more rapidity in the unwashed nectaries. 



If there are old flowers in the Cluster the nectaries of these will prob- 

 ably remain dry after the first washing. But let us remove the nectar from 

 both Clusters again, the one with a pipette and the other by washing and 

 drying as was done at first. The nectar quickly returns in those nectaries 

 where the pipette was used; but in the washed Clusters the fluid does not 

 again reappear unless some of the flowers are very young, in which case 

 a third washing may be required to stop all furlher excretion. 



From the first Cluster we may again and again remove the nectar with 

 pipette, and after each removal it will reappear ; more slowly however 

 after each repetition than on tlxe previous time. 



