38 M. L. Garreau on the Functions of 



The positions it occupies in the cavity of the cell are equally 

 variable ; but its most common place is in the centre of the cell, 

 or adherent to some part of its wall. In the latter case, when 

 the cell is elongated, it is seen to be almost always placed equi- 

 distant from the two extremities ; however, it happens in cells 

 which enter into the structure of hairs, that the nucleus is often 

 seen attached to the septa between them, as in Tradescantia vir- 

 ffinica and Chelidonium majus. 



The constancy of this organ in cells in progress of growth led 

 Schleiden to see in it the explanation of an important fact in the 

 physiology of plants ; and it was in making an attempt to sub- 

 stantiate this conviction that I was prompted to investigate its 

 different forms, some of its properties, and its relations with the 

 walls of the cell. After having submitted anew to the most 

 attentive and minute observation the majority of the tissues that 

 I had already examined, and which had presented me with cells 

 at once sufficiently developed and transparent, I have been able 

 to satisfy myself that the membranous sac of the nucleus whose 

 characters have been detailed above frequently gives off filaments 

 of the greatest softness, and often anastomosing one with another. 

 Many of their slender extremities likewise proceed to coalesce 

 with the layer of nitrogenous material that lines the interior of 

 the cell-wall. In this structural condition I perceived that I 

 had to deal with an important modification of the nucleus, which, 

 instead of being applied directly to the cell-wall, occupied the 

 centre of its cavity, suspended there by the medium of the viscous 

 processes extended from its periphery as just described. Slack 

 and Meyen long since suspected the relations of these filaments 

 (or, as they called them, currents) with the nucleus. Schultz 

 and Hugo Mohl still more distinctly appreciated this relation ; 

 but none of these naturalists would seem to have studied the 

 subject under the most favourable conditions, otherwise they 

 could not have failed to recognize the fact I shall proceed to 

 establish, viz., that these processes are capable in many cells of 

 serving the office of contractile canals for the transmission or cir- 

 culation of a granular fluid. 



On examining, by the aid of a good instrument with a magni- 

 fying power of from 300 to 400 diameters, according to the 

 dimensions of the cells, and at a temperature of 25° to 30° Centi- 

 grade, a slice of tissue the cells of which presents filamentous 

 nuclei (such as those of the full-grown epidermis of the leaves 

 of the Tradescantia virginica, the hairs of Salvia Sclarea, of Cheli- 

 donium, and of Erodium moschatum, procured during the summer 

 or autumn), the observer will not fail to recognize the presence of 

 granules streaming in a transparent fluid through a series of 

 canals formed by an extensible membranous matter, continuous 



