36 M. L. Garreau on the Functions of 



and is less transparent. This change is the consequence either 

 of the action of the reagents upon it, or of the nature of the 

 contained liquid being modified by them. If the flowers of the 

 Tradescantia virginica be selected for observation at the moment 

 when they begin to wither, and when the colouring-matter 

 is diffused within the cavities of the cells, the nucleus may be 

 still more precisely studied in respect to its form and its chemi- 

 cal characteristics. The constituent matter of the nucleus being 

 readily penetrated by the colouring-material, and still more 

 strongly impregnated by it than the surrounding cellulose wall 

 of the cell, it happens that, on moistening the preparation with 

 very dilute hydrochloric acid, the nuclear matter acquires an 

 intense red colour, and is thrown into folds, but presently re- 

 appears under the eye of the observer with a green tint and of a 

 larger size when the acid reagent is saturated by ammonia or by 

 some other soluble base employed in slight excess. Lastly, on 

 following the appearances along the borders of the film of tissue, 

 and on using slight pressure by the glass covering it, some of 

 these small bodies may be detached and forced out through the 

 ruptured cells, when it becomes evident that they scarcely dififer in 

 form or in their nature from mucous globules. It may be added 

 that, if the small body be carefully examined whilst still under the 

 influence of the acid, its centre will be found to be composed of 

 granules strongly condensed into a little mass of a deeper red 

 colour than the softer wall enclosing it, and to which it is fixed 

 by only a single point. From these facts it is at once evident 

 that the nucleus is not a simple collection of particles adhering 

 together, as Brown, Slack, Schultz, and others supposed it to be, 

 but that it possesses a cavity limited by an albuminoid, soft and 

 membranous material, containing granules and a fluid, and that 

 its membrane and granules may be condensed in different degrees 

 by the addition of an acid. 



When similar observations are followed out respecting this 

 particular state of the nucleus in tissues whose cells are of suffi- 

 cient diameter, and their walls transparent enough to permit a 

 just idea of the structure in question to be obtained, then without 

 the help of reagents the above-named facts may be established 

 in the case of most plants, and in all their transparent and actually 

 living parts. But it is a simpler plan, where it is wished only to 

 display the presence of the nucleus, to use a weak solution of 

 iodine in iodide of potassium, which soon tints it of a pale yellow 

 and afterwards of a brown colour. Nevertheless, it is worth 

 noting that this reagent does not act in all plants, or indeed in 

 all parts of a plant, with the same intensity, and that the colour 

 it produces has to be waited for a longer or shorter time, and 

 seems to be influenced by the degree of elaboration of the cellular 



