114 M. L. Garreau on the Functions of 



within the living azotized material flows from the periphery 

 towards the nucleus. 



There likewise exists a centrifugal movement, which goes on 

 by a series of slower contractions, also less marked, and of vari- 

 able rapidity in different canals. The nucleus itself contracts ; 

 but its contractions are slow and gradual, and its movements are 

 only appreciable through its changes in relative position and 

 volume ; for when these contractions take place, it is seen to 

 diminish almost insensibly in magnitude, and to assume a dull- 

 white tint, undergoing at the same moment an inconsiderable 

 amount of displacement. At the least, this organ, suspended 

 like the canals and the viscous currents in the cell-cavity, suffers 

 displacements to a much less limited extent than is generally 

 imagined : this depends on causes inherent in the contractile and 

 extensile properties of the nucleus and its appendages. I have 

 not as yet succeeded in determining whether the granular fluid 

 can return from the centre to the periphery through the whole 

 of the canals that it has traversed to reach the nucleus ; but we 

 may convince ourselves that, among the parallel canals through 

 which the circulation proceeds, it is in some of them centripetal, 

 in others centrifugal. But as the canals are all in connexion 

 with the nucleus, we must assume that this organ is capable of 

 effecting partial contractions, as the canals themselves can do ; 

 for otherwise, if its whole mass were acted upon at the same 

 moment, it would not be conceivable how centripetal and centri- 

 fugal currents should proceed simultaneously. 



The fluid in circulation is ordinarily limpid ; however, in plants 

 having a white latex, such as Campanula pyramidalis, Sonchus 

 oleraceus, &c, it has a certain degree of opacity ; and in Cheli- 

 donium majus, yellowish granules are interspersed within it. 

 Consequently it may at least be supposed, if it be not admis- 

 sible as a legitimate conclusion, that the matters contained in the 

 laticiferous vessels derive their source from the granules of the 

 nutrient fluid within the cell-cavity. The granules carried for- 

 ward in the currents are of two sorts : one, tolerably numerous 

 and nearly spherical, congregates in the nucleus in much greater 

 abundance than in the canals ; the other occurs in molecules of 

 extreme tenuity and less regular in outline, which seem to be 

 slightly more dense than the fluid in which they float ; for in 

 Tradescantia virginica and Erodium moschatum, plants in which 

 they are readily discernible, they are more aggregated at the 

 lower part of the canals than at their centre. 



The nutritive fluid not only moves through the canals which 

 float freely within the cell-cavity, but also in those which con- 

 stitute a network in the primordial membrane, and in those of 

 less size which are obliquely distributed on its internal surface. 



