30 CELL-CONTENTS AND CELL-WALLS. 



29. Cyclosis in Elodea. Mount in water a few leaves 

 of Elodea, which grows abundantly in many rivers and 

 canals, having long submerged stems and leaves arranged 

 in whorls of three. Look for the streaming of the proto- 

 plasm in the leaf -cells. The long narrow cells of the 

 midrib show a continual rotation, which by careful fo- 

 cussing is seen to be confined to the inner portion of the 

 " primordial utricle " this portion of the protoplasm 

 flows round the lateral and end walls of the cell, carrying 

 with it the chloroplasts. The outer portion, in immediate 

 contact with the cell- wall, is at rest, as is also the whole 

 protoplasm layer lying along a line (" indifferent " or 

 "neutral" line) in the middle of the upper and lower 

 walls these points are more easily seen in Nitella or 

 Chara. 



In the shorter and broader cells on each side of the 

 midrib there are strands of protoplasm running across 

 the vacuole, some being attached to the central nucleus ; 

 in these cells the strands, as well as the primordial utricle, 

 show streaming movements in all directions these move- 

 ments of circulation may also be seen in the staminal 

 hairs of Tradescantia ( 31). 



30. Cyclosis in the Stoueworts. Examine specimens 

 of Chara and Nitella, which grow in stagnant or sluggish 

 water, rooting in the mud and sending up shoots often a 

 foot long which bear whorls of appendages ("leaves"). 

 Each " internode " contains a single very long cell, but in 

 Chara this is covered by a layer of cortex filaments (ex- 

 cept in the terminal cells of the "leaves") the rotation 

 can be observed in these naked "leaf" cells of Chara or 

 (better) in the long naked internodal cells of Nitella, 

 which has no cortex. 



Note that here the chloroplasts, which lie in the outer 

 layer of protoplasm just within the cell- wall, remain 

 stationary ; the movement, which is confined to the 

 colourless inner layer, is shown by the sweeping along of 

 the granules embedded in this inner portion of the pro- 

 toplasm. Note the very conspicuous " indifferent line " 

 which runs spirally along the cell and is sharply defined 



