CYCLOSIS IN VEGETABLE CELLS. 395 



all found to have one common point of departure and return, 

 namely, the Nucleus (b, a) ; from which it seems fairly to be" in- 

 ferred that this body is the centre of the Vital Activity of the 

 cell.* Mr. Wenham states that in all cases in which the Cyclosis 

 is seen in the Hairs of a Plant, the Cells of the Cuticle also display 

 it, provided that their walls are not so opaque or so strongly 

 marked as to prevent the movement from being distinguished. 

 The Cuticle may be most readily torn off from the stalk or the 

 midrib of the Leaf ; and must then be examined as speedily as 

 possible, since it loses its vitality when thus detached much sooner 

 than do the Hairs. Even where no obvious movement of particles 

 is to be seen, the existence of a Cyclosis may be concluded from the 

 peculiar arrangement of the molecules of the Protoplasm, which 

 are remarkable for their high refractive power, and which, when 

 arranged in a ' moving train,' appear as bright lines across the 

 Cell ; and these lines, on being carefully watched, are seen to alter 

 their relative positions. The leaf of the common Plantago (Plan- 

 tain or Dock) furnishes an excellent example of Cyclosis ; the 

 movement being distinguishable at the same time both in the Cells 

 and in the Hairs of the Cuticle torn from its stalk or midrib. It 

 is a curious circumstance that when a plant which exhibits the 

 Cyclosis is kept in a cold dark place for one or two days, not only 

 is the movement suspended, but the moving particles collect 

 together in little heaps, which are broken up again by the separate 

 motion of their particles, when the stimulus of Light and Warmth 

 occasions a renewal of the activity. It is well to collect the speci- 

 mens about midday, that being the time when the rotation is most 

 active; and the movement is usually quickened by artificial "Warmth, 

 which, indeed, is a necessary condition in some instances to its 

 being seen at all. The most convenient method of applying this 

 warmth, while the object is on the Stage of the Microscope, is to 

 blow a stream of air upon the thin-glass cover, through a glass or 

 metal Tube previously heated in a Spirit-lamp. 



290. The walls of the Cells of Plants are frequently thickened 

 by internal deposits, which may present very different appearances 

 according to the manner in which they are arranged. In its 

 simplest condition, such a deposit forms a thin uniform layer over 

 the whole internal surface of the Cellulose-wall (probably on the 

 outside of the Primordial Utricle), scarcely detracting at all from 

 its transparence, and chiefly distinguishable by the ' dotted ' ap- 

 pearance which the membrane then presents (Fig. 198, a). These 

 dots, however, are not pores, as their aspect might naturally 



* The above statement is called in question by Mr. Wenhani, who 

 affirms that " whenever he has observed such a ' nucleus ' it has either 

 been formed by an accidental conglomeration of some of the cell-con- 

 tents, or by morbid conditions." The Author is satisfied, however, from 

 the constancy with which the ' nucleus ' is the centre of the diverging 

 lines of protoplasm, in those cells which have several streams radiating 

 from one point, that it can neither be an accidental nor a morbid con- 

 glomeration. 



