CELLS IN LOWER PLANTS. 95 



The cjrtoplasm in a fresh Vaucheria filament will, if watched, 

 and especially if the slide be warmed, be found to exhibit the 

 phenomenon of " rotation '' or streaming, similar to that which 

 was observed in the cells of Vallisneria (Chapter ii.). 



Flasmolysis is very striking in Fauckeria, On the addition of 

 a drop of 20 per cent, acetic acid or strong salt solution, the 

 cytoplasm retracts from the wall, bridles at first connecting the 

 retracted portion with the cell-wall ; ultimately the protoplasm 

 forms a retracted axial cord, the oil-globules being often forced 

 out of it and lying between it and the wall of the filament 

 (see Fig. 73, 2). 



Faucheria is often reproduced by an asexnal method — viz., 

 by means of swarmspores — which may be described at this 

 point. A portion of the cytoplasm with several nuclei and 

 chloroplasts is cut off from the free end of the filament by the 

 formation of a thin partition wall. This mass of cytoplasm soon 

 acquires a delicate external layer of ectoplasm, and from this 

 latter numerous short vlbratile cilia arise.* The cellulose 

 wall at the free end of the filament then ruptures and sets 

 free this swarmspore, which at once begins to move rapidly 

 through the water by means of its cilia. At a certain period, 

 however, it becomes fixed by one extremity to an object, the 

 ciha vanish, and the cytoplasm develops a wall of cellulose. 

 After a period of quiescence this "encysted" spore becomes 

 active and produces a fresh Vaucheria filament, the thick wall 

 bursting and the cytoplasm growing out into an elongated mass 

 which is soon coated by a thin wall of cellulose. The nuclei and 

 chloroplasts also undergo division, and soon a typical filament 

 is reproduced. 



The sexual method of reproduction will be described in 

 Chapter ix. 



c. Sphxrella. — This organism occurs in several forms, and 

 the one which will be described here is known as Sphmrella 

 phvialis, occurring in pools of rain-water which have lain a 

 few hours. 



Sphcerella, in its free-swimming stage, is a motile cell, the 

 motility being consequent on the possession of two vibratile 



* Pairs of these cilia arise just opposite each of the numerous nuclei, 

 which latter are arranged in line all round, immediately internal to the 

 outer firm boundary. 



