Natural History. 389 



opposite direction to the first horizontal motion, and again ascend 

 as before. This effect continues as long as the plant is alive. All 

 the globules are not in contact with the surface of the tube ; those 

 which are at some little distance, circulate as well as the others, 

 but less rapidly ; and their motions were slower, as they were 

 nearer to a plane, which may be supposed to pass through the 

 tube, and separate the two currents. Sometimes the globules dis- 

 placed each other, at other times they passed from the one side to 

 the other, before they reached the diaphragm. The directions of the 

 motion in two parallel and contiguous vessels appeared to have no 

 relation to each other. The rapidity is variable, according to the 

 size and length of the canal, and the degree of injury it may have 

 suffered in preparing it, a complete circulation has been observed in 

 a vessel ^ of a line, in length, in 30", this velocity is not more than 

 a third of that observed in the chara vulgaris. It is to be remarked 

 that when the plant is cut, to submit it to observation, the circulation 

 is suspended for a time and requires some hours to be renewed. 



The circulation of the sap takes place in the cellular tissue as 

 well as in the vessels, the globules move along the surface of the 

 cell, changing their direction when they arrive at the angles of the 

 polygons. Sometimes a mass of globules collect in the centre and 

 rotate with a motion common to the whole. Observations on the 

 leaves are more delicate, than those on the stalks of the plants, they 

 require to be made whilst the leaf is attached to the plant, and the 

 light must be thrown from above, as for opaque objects. 



Thus each vessel presents two currents, one ascending, the other 

 descending, which are not separated by any division : the interior 

 is studded with small crowns, composed of particles which are very 

 difficult to discover, because of their tenuity and transparency, and the 

 nature of the motion shews it to arise from the surface of the tube, and 

 precisely from those points occupied by the crowns, for there may be 

 observed the maximum of the velocity with which the globules move. 



M. Amici docs not state that no liquid passes from one cavity to 

 another, he is indeed convinced of the contrary ; but the transfusion 

 takes place through invisible apertures, through which the globules 

 cannot pass. He has remarked two varieties of limpid fluid in the 

 Caulinea, one white and one red, contained in different vessels, though 

 of the same form. He attributes the distinct green colour of the 

 plant, to globules very green themselves, floating in the fluid ; they 

 are greener towards the exterior of the plant, than in the interior. 

 There is this difference between the Chara and the Caulinea, that in 

 the first the globules are white, and the particles of the small crowns 

 green, the latter colour the plant ; but in the second, the globules are 

 green, and the crowns yellow. Oil and alcohol do not alter the 

 form of the globules of the Caulineabut discolour them entirely. 



Chara Jhxilis. The organization of this plant is exceedingly sim- 

 ple, a section of the root, the trunk, the branches, or the leaves, pre- 



