in the Interior of Cells. 7 



loped, and others from flowers which had just opened*. This 

 movement took place so slowly that the nucleus required from 

 a quarter to half an hour to pass through one-third or half 

 the longitudinal axis of the cell, progressing not more than 

 about 7 jo o tn °f a P ar i s nnc m a second. A somewhat slower 

 motion, the velocity of which however I forgot to measure, in 

 which the nucleus glided along the cell- wall, was observed in the 

 linear primordial leaves of Sagittaria sagittifolia ; the same may 

 be very readily observed in the leaves of Vallisneria spiralis, the 

 nucleus here following the current of sap with the same velocity 

 as the granules of chlorophylle. The following phenomena, 

 which I observed on the stinging hairs of Urtica baccifera, yield, 

 together with this change of position of the sap current and 

 nucleus, a further proof against the existence of a vascular system 

 or inner cells. I left a leaf of this plant lying for a couple of 

 days on the table, so that with the exception of the large ribs 

 and the stinging hairs situated on it, it was perfectly dry. Now 

 in these faded hairs the currents appeared to be very much 

 altered ; some still existed in the natural state and were in mo- 

 tion, but in the greater portion the granules had separated and 

 were distributed with tolerable uniformity over the surface of the 

 cellular membrane, and exhibited a molecular motion. When 

 some of the hairs which had been cut off had lain in water for 

 half an hour and were again full of sap, the granules arranged 

 themselves more and more into filaments, between which were 

 some free spaces and in which the circulating motion was com- 

 pletely restored. In this case, therefore, every possibility of the 

 currents being inclosed between membranes is excluded ; indeed 

 the form of the currents of sap, as exhibited in the stinging hairs 

 of this plant, is opposed to that view. 



The movement of the current is mostly very irregular ; if we 

 leave Chara out of the question, it is most regular in Vallisneria, 

 but even here it is far from being uniform. The sap flows 

 quicker in one cell than in another, in one current quicker 

 than in the adjacent ; frequently stoppages occur at some spots, 

 so that the sap becomes increased for a time, and some granules 

 arc overtaken by those behind them, &c. This inequality of the 

 motion renders the determination of the velocity of the current 



* It may perhaps be of interest to those persons who may wish to observe 

 the circulation of the sap in the hairs of Tradescantia if I describe a mani- 

 pulation by means of which the layer of air which adheres tenaciously to the 

 surface of the hairs when they are placed in water may be removed, as it 

 diminishes the transparency of the hair and renders the observation more 

 difficult. For this purpose it is only necessary to dip the filament with its 

 hairs for a moment in alcohol, and to wash this off again immediately with 

 water, when the disturbance is got rid of without the circulation of the sap 

 being modified. 



