272 Mr. W. Gardiner. On the Continuity of the [Nov. 16, 



structure. Granting that light is the cause of distension propor- 

 tionate to functional activity and in excess of the passive properties of 

 the tissue, the pulvinar tissues throughout during the incidence of 

 light will contain a functional excess of liquid, and the withdrawal of 

 light will lead to a general diminution of distension — the non-illumi- 

 nated tissues parting with the functional excess of fluid, and retaining 

 merely the amount proportional to their diminished activity. But 

 those portions of tissue providing the greatest facilities for redistribu- 

 tion of fluids must, other things being alike, tend most rapidly to 

 arrive at their passive condition of tension. In the pulvini, then, it is 

 quite possible that those portions of tissue which are characterised by 

 excessive diurnal activity and functional distension may attain their 

 passive condition sooner than the others do, due to their respective 

 structural peculiarities. But from the period at which the one part 

 of the pulvinus has attained its passive condition until the other has 

 also done so, a continuous alteration in their relative tensions must 

 take place. Those portions of tissue which tend to the assumption of 

 the diurnal position will, according to this, on the onset of darkness, 

 rapidly attain their maximum relative weakness, and after this will 

 become relatively stronger until the opposing portions have also 

 arrived at their passive condition of tension. An early development 

 of the maximum nocturnal position, and a subsequent reversion 

 towards the diurnal one, such as actually occurs, might therefore be 

 looked for on a priori grounds. Nocturnal reversion may probably 

 in great measure be thus explained, but, as indeed in the case of 

 other movements, other factors such as variations in the absolute 

 weight and consequent leverage of various parts of the leaves con- 

 nected with variations in amount of respiration and assimilation no 

 doubt come more or less into play. 



IV. On the Continuity of the Protoplasm in the Motile Organs 

 of Leaves." By Walter Gardiner, B.A., late Scholar of 

 Clare College, Cambridge. Communicated by Dr. M. 

 Foster, Sec. R.S. Received November 11, 1882. 



In a preliminary note published in the " Quarterly Journal of 

 Microscopical Science," for October, 1882, I stated that I had suc- 

 ceeded in demonstrating that the continuity of the protoplasm of 

 adjacent cells in the pulvinus of Mimosa pudica was maintained by 

 protoplasmic filaments, which passed through pits in the cell wall. I 

 have since then shown that the same occurs in Robinia and Amicia.. 

 In Phaseolus the connexion is much less pronounced, and as yet I 



