6 M. Mohl on the Circulation of the Saji 



solved in the liquid filling these cavities possessing a great re- 

 fractive power, and which subsequently again disappears, or whe- 

 ther the phenomenon is due to other causes, I have not been able 

 to ascertain. 



When the protoplasma has assumed the form of filaments, a cur- 

 rent may almost always be observed in them. This may of course 

 be easily detected when readily perceptible globules are contained 

 in the currents, as in the filamentary hairs of Tradescantia, in the 

 stinging hairs of Urtica, in the hairs of the melon, &c. ; but where, 

 on the contrary, this is not the case, and the filaments consist 

 of a very homogeneous transparent mass, as for instance in the 

 hairs of Alsine media, the existence of the current can only be 

 inferred from the change of position in the filaments. With re- 

 spect to this alteration in the position of the currents, the cessation 

 of some and the origin of others at fresh places where none pre- 

 viously existed, this phenomenon had been already described by 

 others, especially by Meyen and Schleiden, so accurately, that it 

 would appear quite unnecessary to mention it here were it not 

 for the sad reality, that in opposition to all the earlier and very 

 accurate observations, the correctness of these observations have 

 not merely been denied with the most positive certainty by two 

 parties quite recently, but that perfectly untenable theories have 

 been advanced of the perforation of the cell-walls by the milk 

 sap-vessels in which the currents described are said to occur, or 

 of secondary cells contained in the cell-cavity in whose inter- 

 cellular spaces the granular fluid is said to be contained. The 

 assumption of solid tubular or membranous formations in or be- 

 tween which the moving fluid is said to be contained, must be 

 entirely rejected by every one who has had an opportunity of 

 convincing himself of the variability of these currents, and any 

 observation made with tolerable care will soon yield this conviction 

 most satisfactorily. It has frequently happened to me, that even 

 in the short time which I required for drawing the currents con- 

 tained in a cell, for instance of Tradescantia, their position and 

 number were essentially altered \ but not merely the delicate cur- 

 rents which run free through the cell-cavity or along its walls 

 alter their position, but in many cases even the position of the 

 nucleus, when it is situated in the axis of the cell in the midst 

 of the mass of currents which run from the centre of one hori- 

 zontal wall to the centre of the opposite one, is subjected to a 

 slow but still very decided change. I have observed this mo- 

 tion taking place in the direction of the axis, alternately ascend- 

 ing and descending, and repeated in a very decided manner, 

 on the filamentary hairs of Tradescantia Sellowiana, some of 

 which I took from buds which were not more than half deve- 



