LIFE OF THE PLANT-CELL. 97 



is scarcely at all observable. May not this motion be regarded as a 

 universal phenomenon, and as most intimately connected with the assi- 

 milation of the azotized matters ? 



Historical and Critical. This form of sap-motion was discovered 

 by Robert Brown in 1831, in the hairs of the filaments of Tradescantia 

 virginica* Slack, Meyen, and myself, have contributed the principal 

 additions to the number of instances. Meyen thinks that, besides these 

 sap-currents, air is contained in the hair- cells in T. virginica; but 

 this is altogether erroneous. His attributing an assertion to the same 

 effect to Robert Brown f, arises simply from a mistranslation of the 

 English : Robert Brown refers merely to the air which is adherent to 

 the hairs. Slack \ supposed that the hair-cells of T. virginica contain 

 a second utricle, and that the currents flow between its wall and that of 

 the cell. Accurate observation easily shows this view to be a mere 

 fiction. The most superficial observation only, or the most defective 

 microscope, could have led Schultz to misplace these currents on the 

 outside of the cell, in a special system of vessels (his " vasa laticis con- 

 tracta"). A single attentive observation is sufficient to refutet his notion, 

 and to demonstrate the phenomena as I have described them, as well as 

 the impossibility of the existence of such a system of vessels. Meyen 

 ascribes the motion not to the fluid, but to a self-motive power inherent 

 in the granules that are carried round with it ; an idea which, in some 

 cases, has led to his overlooking the fluid. But views of this kind I regard 

 as being without any foundation whatever. 



I make no reference to the dispute as to the existence of either this or 

 the previously described motion, any question upon the subject being 

 altogether out of date. Whoever, at the present day, entertains a doubt 

 about it, is quite unfit to make any physiological observation. 



42. The spiral filaments in the antheridia of the Characece, 

 Mosses, Hepaticce, and Ferns, mentioned at the end of 39., ex- 

 hibit, at least when in contact with water, a peculiar motion, con- 

 sisting principally in a rotation around the axis of the spiral, and 

 which motion in the free filaments is shortly changed (according 

 to the law of the Archimedean screw) into a progressive movement ; 

 but the motion is modified in divers ways, according to the varying 

 width and diameter of the spirals. 



The motion referred to in the section is as yet, together Avith the 

 existence of vibratile cilia, one of the most remarkable and mysterious 

 phenomena in the vegetable world. Phenomena of this kind afford but 

 too ready a ground for the unbridled fancy to fill up the defective gaps 

 in our knowledge, with what are termed clever notions; the divine 

 maxim of St. Paul, " that we know in part," being disregarded. Many 

 fabulous statements consequently have, in former times, been made 

 on this subject. Too much caution, therefore, cannot be employed 

 when apparent analogies are indicated, lest they should be received 

 as views having a scientific foundation, and used in the erection of a 



* On the Sexual Organs, &c. in the Orchides-e and Asclepiadeae (1831), p. 172. 



f Physiologic, Bd. II. S. 244, et seq. 



\ Transactions of the Society of Arts, &c., vol. xix. (1833). 



Flora, 1834, p 120., and his Paris prize essay upon " Cyclosis." 



H 



