CYCLOSIS OF PROTOPLASM 689 



in the Characete (see p. 564), and which consists in the steady flow 

 of one or of several currents of protoplasm over the inner wall of 

 the cell, this being rendered apparent by the movement of the 

 particles which the current carries along with it. The best exam- 

 ples of it are found among submerged plants, in the cells of which it 

 continues for a much longer period than it usually does elsewhere ; 

 and among these are two, TW//-s//' //'/ x/>ii-<ilis and Anacharis alsi- 

 nastnun (or Elodea canadensis), which are peculiarly fitted for the 

 exhibition of this interesting phenomenon. Vallisneria is an aquatic 

 plant that grows abundantly in the rivers of the south of Europe, 

 but is not a native of this country ; it may, however, be readily 

 grown in a tall glass jar having at the bottom a couple of inches <it' 

 mould, which, after the roots have been inserted into it, should be 

 closely pressed down, the jar being then tilled with water, of which 

 a portion should be occasionally changed. 1 The jar should be freelv 

 exposed to light, and should be kept in as warm but equable a tem- 

 perature as possible. The long grass-like leaves of this plant are too 

 thick to allow the transmission of .sufficient light through them for 

 the purpose of this observation, and it is requisite to make a thin 

 slice or shaving with a sharp knife. If this be taken from the 

 surface, so that the section chiefly consists of the superficial layer of 

 cells, these will be found to lie small, and the particles of chlorophyll. 

 though in great abundance, will rarely be seen in motion. This 

 layer should therefore be sliced off (or perhaps still better, scraped 

 away) s > as to bring into view the deeper layer, which consists of 

 larger cells, some of them greatly elongated, with particles of chloro 

 phyll in smaller number, but carried along in active rotation by the 

 current of protoplasm ; and it will often be noticed that the direc- 

 tions of the rotation in contiguous cells are opposite. If the move- 

 ment (as is generally the case) be checked by the shock of the 

 operation, it will be revived again by gentle warmth ; and it may 

 continue under favourable circumstances, in the separated fragment, 

 for a period of weeks, or even of months. Hence, when it is desired 

 to exhibit the phenomenon, the preferable method is to prepare the 

 sections a little time before they are likely to be wanted, and to 

 carry them in a small vial of water in the waistcoat pocket, so that 

 they may receive the gentle and continuous warmth of the body. 

 In summer, when the plant is in its most vigorous state of growth, 

 the section may be taken from any one of the leaves ; but in winter 

 it is preferable to select those which are a little yellow. An objec- 

 tive of J-inch focus will serve for the observation of this interesting 

 phenomenon, and very little more can be seen with a ^-inch : but 

 the -/--inch constructed by Messrs. Powell and Lealand enables the 

 borders of the protoplasmic current, which carries along the 

 particles of chlorophyll, to be distinctly defined ; ami this beautiful 



1 Mr. Quekett found it the most convenient method of changing the water in the 

 jars in which Ckara, Valli&neria, &c., are growing, to place them occasionally under 

 a water-tap, and allow a very gentle stream to fall into them for some hours ; for by 

 the prolonged overflow thus occasioned all the impure water, with the Conferva that 

 is apt to grow on the sides of the vessel, may be readily got rid of. 



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