108 LAY SERMONS, ESSAYS, AND REVIEWS. [vn. 



parts of the protoplasm take similar directions ; and, thus, there 

 is a general stream up one side of the hair and down the other. 

 But this does not prevent the existence of partial currents 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 ; while, occasionally, oppo 

 site streams come into direct collision, and, after a longer or 

 shorter struggle, one predominates. The cause of these currents 

 seems 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 prisoned 

 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 its display, continued hour 

 after hour, without pause or sign of weakening. The possible 

 complexity of many other organic forms, seemingly as simple 

 as the protoplasm of the nettle, dawns upon one; and the 

 comparison of such a protoplasm to a body with an internal 

 circulation, which has been put forward by an eminent physio 

 logist, loses much of its startling character. Currents similar to 

 those of the hairs of the nettle have been observed in a great 

 multitude of very different plants, and weighty authorities have 

 suggested that they probably occur, in more or less perfection, in 

 all young vegetable cells. If such be the case, the wonderful 

 noonday silence of a tropical forest is, after all, due only to the 

 dulness of our hearing ; and could our ears catch the murmur of 

 these tiny Maelstroms, as they whirl in the innumerable myriads 

 of living cells which constitute each tree, we should be stunned, 

 as with the roar of a great city. 



Among the lower plants, it is the rule rather than the excep 

 tion, that contractility should be still more openly manifested at 

 some periods of their existence. The protoplasm of Algce and 

 Fungi becomes, under many circumstances, partially, or com 

 pletely, freed from its woody case, and exhibits movements of its 

 whole mass, or is propelled by the contractility of one, or more, 



