II 



and roughly corresponding in form with the interior of 

 the hair which it fills. When viewed with a sufficiently 

 high magnifying power, the protoplasmic layer of the 

 nettle hair is seen to be in a condition of unceasing ac- 

 tivity. Local contractions of the whole thickness of its 

 substance pass slowly and gradually from point to point, 

 and give rise to the appearance of progressive waves, 

 just as the bending of successive stalks of corn by a 

 breeze produces the apparent billows of a corn-field. 

 But, in addition to these movements, and independently 

 of them, the granules are driven, in relatively rapid 

 streams, through channels in the protoplasm which seem 

 to have a considerable amount of persistence. Most 

 commonly, the currents in adjacent parts of the proto- 

 plasm take similar directions j and, thus, there is a gen- 

 eral stream up one side of the hair and down the other. 

 But this does not prevent the existence of partial cur- 

 ' rents which take different routes ; and, sometimes, trains 

 of granules may be seen coursing swiftly in opposite 

 directions, within a twenty-thousandth of an inch of one 

 another j while, occasionally, opposite streams come 

 into direct collision, and, after a longer or shorter strug- 

 gle, one predominates. The cause of these currents 

 seem to lie in contractions of the protoplasm which 

 bounds the channels in which they flow, but which are 

 so minute that the best microscopes show only their 

 effects, and not themselves. 



The spectacle afforded by the wonderful energies pris- 

 oned within the compass of the microscopic hair of a 

 plant, which we commonly regard as a merely passive 

 organism, is not easily forgotten by one who has watched 



