14 OF VITAL MOTION. 



in another instance it follows a spiral course in a 

 transverse direction : in a third it is vague, and to 

 all appearance unobservant of any particular law. 



In attempting to detect the causes of these several 

 movements, we propose to commence our task with 

 the study of the phenomena of cyclosis, for here we 

 secure an intermediate position between the vague 

 and imperfectly-understood movements confined to 

 individual cells, and that more complicated circulation 

 of the sap which extends to the entire plant. 



I. OF THE MOVEMENTS IN THE MILK VESSELS OF 

 THE PLANT (CYCLOSIS). 



In this, as in every phenomenon of vital movement, 

 we have to seek for the efficient cause in agents which 

 proceed from surrounding objects, and in agents which 

 reside within the organism. 



1. Of extra-organic force as the agent in the 

 phenomena of cyclosis. 



On watching the movements of the sap in the 

 laticiferous vessels, Dr. Lindley found them to cease 

 in a low temperature, and to recommence when the 

 plant was carried into a warm room ; and in this fact 

 we have evidence of a partial dependence upon the 

 influence we designate as heat. Let us begin our 

 examination, then, by inquiring into the manner in 



