34 M. L. Gavreau on the Functions of 



organism, formed by a closed membrane, capable of self-increase, 

 of self-multiplication, and of absorbing and transmitting by en- 

 dosmosis fluid materials destined to nourish it. This definition, 

 though true in all its details when an examination is conducted 

 by the aid of too feeble or of too strong magnifying powers, or 

 when experiments are conducted on dead tissue, cannot be 

 entirely sustained when the investigation is pursued by appro- 

 priate amplifying powers, and when the still living organization 

 is submitted to observation ; for, under such circumstances, it 

 becomes possible to demonstrate that the vegetable cell is not so 

 simple in its structure as has been presumed, nor so independent 

 as supposed when it enters into the composition of a tissue. But 

 notwithstanding that the cell is everywhere, whether isolated or 

 aggregated with others, essentially the same in its organization, 

 it is necessary, in order to its minute examination, to employ 

 those portions of plants in which an active process of vegetation 

 is proceeding, — where intra-cellular secretions are absent, and 

 the cellulose and encrusting matters have not as yet so thickened 

 the tissues as to impede the thorough examination of the cell- 

 cavity. 



If a slice of vegetable tissue be taken, so thin as to consist of 

 not more than two superposed rows of cells (conditions readily 

 realized in hairs, in the tissue of spongioles, in the lamina of 

 fleshy leaves, in young epidermis^ in the pith, in the parenchyma 

 of young petioles, in various fruits, &c.), and if this be examined 

 in a moist state, at a temperature of from 20° to 35° Centigrade, 

 the microscope quickly reveals a small conglomerate mass in each 

 cell, often granular in aspect, and attached to some part of its 

 inner wall. Such is the little body designated by Robert Brown 

 as the nucleus, and which he regarded, as did also Schleiden and 

 Hugo Mohl, as a structure existing prior to the formation of the 

 cell-wall. It was moreover looked upon by these naturalists, 

 together with Schultz, Slack, and Meyen, as constituted by the 

 more or less intimate aggregation of nitrogenous granules. 



However, this little organ is not entirely formed by the reunion 

 of agglomerated granules, and one might be easily led into error 

 in making researches for its elucidation if it was assumed that it 

 was always to be met with under the aspect above mentioned ; 

 for in the majority of the simple hairs of herbaceous plants, in 

 epidermis, and in nearly all young tissues, it occurs under the 

 form of an opaline globule, variable in dimensions, and refracting 

 light much in the same way as fatty matters. Further, under 

 an irregular form, it frequently presents itself in the sub-epider- 

 mic cells of leaves, infiltrated with chlorophyll and with some 

 granules in its middle. Again, in young cells, and in pollen in 

 course of growth, it appears formed of flakes loosely coalesced into 



