48 WENHAM, ON THE SAP-CIKCULATION OF PLANTS. 



numberless instances in both the cells and hairs of plants. 

 An isolated active corpuscle is seen detached, quickly per- 

 forming its vibrations with constant activity, until its progress 

 becomes arrested by one of the various ramified currents which 

 traverse tiie hair; at which instant the vibratory movements 

 totally cease, and the particle visibly assists the direct-forward 

 motion of the current by its vital energy. 



I observed with regard to the ArMcharis, that after having 

 been kept in a cold, dark place for one or two days, usually 

 not a symptom of circulation could be discovered, the cor- 

 puscles Laving collected together in heaps, with the component 

 particles in a state of torpidity, and on being again exposed 

 to the stimulus of light and heat, they recommenced their 

 active motions. This effect is still more remarkable in some 

 non-aquatic plants ; and a practised eye may at once detect, by 

 the state of the cell-contents, whether the plant is in a state 

 of repose or hybernation, as the corpuscles will in this case 

 be seen collected together in several gelatinous-looking clots, 

 their dormant vitality being again called into existence, by 

 the same method as described for the Anacharis. Light is 

 also quite as necessary a stimulus as heat ; for in a recent 

 experiment on this plant I interposed four thicknesses of blue 

 glass between the achromatic condenser, and luminous source, 

 (bright skylight,) thus entirely intercepting the heating rays, 

 and yet, in spite of this intervening obstacle, speedily suc- 

 ceeded in exciting the movements of circulation. 



The microscope discovers that in every portion of the plant 

 each duct, cell, or vesicle, that is filled with sap, also contains 

 active corpuscles, apparently differing in dimensions and 

 substance according to locality. As regards tl)e office that 

 these bodies fulfil, it may be inferred that either they are the 

 vehicles that convey nourishment to different portions of the 

 cell-tissues, or that they themselves are deposited, to form 

 the various structures of the plant. I will give an illustra- 

 tion of the latter effect. The annexed woodcut represents one 

 of the liairs or spines taken from the stalk of the Anchusa 

 paniculata (Borar/inacece), an ornamental flowering plant of 

 rapid growth. The growth of the spine is performed by the 

 addition of successive layers to the interior, as shown at a, a, 

 which eventually fill up the apex and render it solid : the 

 method by which this action takes place is as follows : — A 

 dense current of corpuscles are seen to travel along one wall 

 of the spine, constantly returning by the opposite side, repre- 

 sented at h h. At c, where the deposition occurs, there is a 

 considerable accunmlation, and at the boundary, where they 

 are converted into the substance of the spine, a number are 



