PLANT LIFE IN PONDS & STREAMS 



mass of granular living substance. At the forward 

 end of the plant, there is a clear space and near the 

 tip a brownish dot, known as the eye spot; which, 

 though incapable of seeing as we understand it, is 

 sensitive to light, as shown by the fact that the 

 little plant will swim towards moderately intense 

 light and away from strong light. If we stain the 

 plant with iodine we can plainly see a pair of 

 little whips arising from the clear portion at the 

 forward end ; it is by the lashing of these that the 

 plant is enabled to swim. 



In the mud of our pond we may find a little colony 

 of plants which might forgivably be mistaken for 

 a collection of the individuals we have just studied. 

 Each member of the colony is very much smaller 

 than Chlamydomonas to be sure, but each one has 

 the outer membrane, the brownish eye spot and the 

 pair of little whips. On the other hand the chloro- 

 phyll fills the whole of each cell and is not arranged 

 in the form of a cup. Sixteen cells form a colony, 

 and the whole mass is a fiate plate ; the little whips 

 move in unison and the whole colony revolves after 

 the manner of a wheel. 



Another little colony we may encounter also, 

 consists likewise of sixteen cells very like the ones 

 we have described, but somewhat wedge-shaped 

 instead of oval. A jelly-like mantle encloses the 

 colony and, in outline, it is spherical, so that when 

 the little whips, which project through the mantle, 

 lash the water the whole colony revolves. 



The most remarkable of these colonies of cells is 



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