116 



ON THE PLANT-CELL. 



J02 



existence of the motion of the latex, but merely to show that the mode in 

 which this subject has hitherto been treated cannot lead to any useful 

 scientific result. 



When the facts themselves are consulted we must accurately divide 

 them into two sets ; those which are derived from the prepared, and those 

 from the uninjured, plant. It must, moreover, here be remarked that in 

 the very young condition only a clear watery fluid is contained in the 

 latex-vessels, and consequently that it is impossible to observe any 



motion in it ; and that in ves- 

 sels of a certain age, and with 

 thick walls, the latex coagu- 

 lates in many ways, and is 

 transformed into a solid mass, 

 as, for instance, in the Eu- 

 phorbiacce. The question re- 

 specting a motion can only 

 arise principally with respect 

 to vessels of an intermediate 

 age. Under these circum- 

 stances, when a section is 

 placed under the microscope, 

 a rapid motion is noticed in 

 the, for the most part granu- 

 lar, sap *, frequently in oppo- 

 site directions. Upon looking 

 at the extremities of the cut 

 vessels, a protruded and coa- 

 gulated mass will be found at 

 each end of the same vessel, 

 and at the same time an outward current will be remarked at each side 

 or the commencement of such a current at one side ; and when the 

 escape of the fluid is stayed at this point by the coagulum, immediately 

 after its cessation, an outward current will be established on the other 

 side : so that it is impossible, without a preconceived notion, to regard 

 this motion as it appears in these observations as one having a deter- 

 minate direction. 



In uninjured plants, the motion of the latex can very seldom be suc- 

 cessfully shown : even in Chelidonum ma jus it is only occasionally pos- 

 sible, and then presents great optical difficulties. It is easy, on the other 

 hand, to observe it in Alisma Plantago. In this case a motion is un- 

 doubtedly visible, viz. a current sometimes more rapid, sometimes slower, 

 and, in the same vessel, sometimes in one direction, sometimes in the 

 other, but frequently alternating with very long periods of quiet. Of a 

 regular motion in a determinate direction, I have never been able to ob- 

 serve any indication. What I have just stated, then, may in general 

 terms be said to include all that I have been able to arrive at as a certain 

 result, from the most careful observations made on the most different 



* Meyen, who at one time saw cells everywhere as Muscos volitantes, also regarded 

 these granules in the same light. They are, however, decidedly consistent, solid 

 granules. 



102 Latex-vessel from the leaf of Limnocharis Humboldti. At the commencement cf 

 the observation, the upper end (a) emptied itself and collapsed. The arrows indicate 

 the observed direction of the outward current. Every latex-vessel is bordered by two 

 rows of narrow, somewhat elongated, parenchymatous cells (&). 



