BRANSON, ON CILIARY ACTION. 275 



or paper will very soon be drawn to the edge. Now the 

 cork in this case bears about the same proportion to the basin 

 of water which the granule of chlorophyll does to the cell in 

 which it floats. In the latter case, however, instead of a 

 single gentle wave at one point of the edge of the basin, we 

 have a wave surrounding the whole cell, formed by innu- 

 merable very minute cilia ; and this multiplication of minute 

 forces produces a current of considerable velocity. Of course 

 the current once established becomes quicker and quicker, 

 and is helped onwaid by its own impetus. This exactly 

 explains the appearance presented on the first starting— so to 

 speak — of the circulation in a cell : a granule of chlorophyll 

 is slowly drawn to the edge of the cell, and then slowly moves 

 round it ; another granule follows, until all are at length 

 drawn to tlie edge, and pass round ; the motion then becomes 

 quicker and quicker, until it reaches the limit of its speed. 

 But the ciliary motion is occasionally irregular — slower in 

 some parts ol the line, or perhaps interrupted altogether ; 

 and the consequence is, that the granules accumulate at the 

 weak, or interrupted point, until the re-established ciliary 

 wave again urges them forward. Any one accustomed to 

 watch the circulation in plants must have frequently observed 

 that the granules of chlorophyll become crowded together, and 

 then slowly and singly again move onward. Ciliary action 

 satisfactorily explains this movement. In the cells of the 

 Anachai'is the cilia are arranged in lines around the cell ; 

 occasionally, however, the granules of chlorophyll, instead 

 of passing round the cell, turn off at an abrupt angle, and 

 cross it ; when this is the case a bright line may be observed 

 on the cell wall, and along this bright line the granules pass. 

 This line may be distinctly seen on the cell-wall before the 

 granules are in motion, and, if accurately examined, will even 

 then give an indication of a minute current passing along its 

 course. This bright line is doubtless the base of a line of 

 cilia, but the ciliary wave cannot, under these circumstances, 

 be seen, for the cilia are not in profile. The Anacharis is 

 better adapted to display the ciliary wave than the Valisneria. 

 In the latter it is difficult to slice off a single layer of cells, 

 whilst in the former Nature has prepared a single layer most 

 suitably arranged for observation. The currents seen in the 

 hairs of certain plants differ somewhat from those in which 

 the granules of chlorophyll circulate ; they are more minute, 

 irregular, and weaker. Even whilst observing a hair of the 

 Groundsel currents start into view, which a moment before 

 were not in existence, and as rapidly pass away — others follow 

 a more definite course, and sometimes the whole hair appears 



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