WENHAM, ON THE SAP-CIRCULATION OF PLANTS. 47 



on being' carefully watched, are seen to alter their relative 

 positions, a condition evidently depending upon progressive 

 motion. Most leaf-cells, of course, contain chlorophyll-gra- 

 nules ; I have occasionally seen a few of these kept in a 

 continual motion by the sap-currents, but never in any in- 

 stance with the same degree of vigour and constancy, as in 

 aquatic plants. In the cells of the common Plantain [Plan- 

 tcifjo) a few chlorophyll -granules aie sometimes seen in motion. 

 This plant furnishes an excellent object, as the cuticle from 

 the stalk or midrib of the leaf shows circulation, both in the 

 hairs and cells at the same time : the sap-motions round the 

 latter are occasionally quite as plainly seen as in the Anacharis, 

 but more frequently the current is one of extreme tenuity, 

 and travels round the cell-wall with great velocity. 



In the cells of the Horse Thistle ( (7/«'cM5) I have also seen 

 the chlorophyll-granules carried along with considerable vigour 

 by the sap-currents : this plant exhibits a remarkable variety 

 in the phenomena of circulation. The glutinous corpuscles 

 are connected together in the form of a line, or rope stretched 

 across the cell, exhibiting a loose vibratory motion as if it 

 were being shaken at one end, while particles and, occasionally, 

 chlorophyll-granules, are carried forward in a manner resera- 

 blin": beads along' a strinar. 



Having now noticed some of the distinguishing peculiarities 

 of the circulation in a few of the plants that have come under 

 my observation, I will offer some brief remarks on the vdtal 

 principle of vegetable growth and motion, I had stated in 

 my former paper that the cell-circulation, or what is termed 

 " rotation," in the Anacharis, is entirely caused by the com- 

 bined effort of a multitude of active corpuscles ; the same fact 

 equally applies to every other plant that I have examined ; 

 and subsequent experience has given me some further insight 

 into the nature of these atoms ; they evidently derive their 

 origin and formation from the most fluid portion of the sap, 

 with which every cell is filled, and which pervades all other 

 portions of the plant tissues. In every stage of their growth 

 they individually possess the motion peculiar to active mole- 

 cules, but when in combinaticm in their containing cell, this 

 motion is converted into one of direct progi'ession from some 

 cause that I am not able to explain. I have tried by various 

 means to effect a similar motion artificially in ducts and tubes, 

 with both organic and inorganic active molecules, but without 

 success ; I therefore conclude, that the progressive movement 

 is not due to any mechanical conversion of one force into 

 another, but arises from some unknown property, connected 

 with the vitality of the plant. I have witnessed the effect in 



