and Exfoliation in the Roots of Plants. 205 



speedily exfoliate. These elongated cells, taken in the adult 

 condition, are devoid of large granules; but their living substance 

 presents itself then in the form of a nucleus connected with the 

 internal membrane by filaments in which exist rapid currents 

 conveying granules of extreme tenuity. Subsequently, when 

 the cell has acquired its full size, the substance of the currents 

 and the nucleus becomes divided, in each cell, into two or three 

 masses, of oval form, which soon constitute two or three cells 

 placed end to end, but which ultimately separate from one 

 another. 



The radicles of millet, barley, buckwheat, beans, clover, 

 lentils, vetch, wild chicory, Crepis virens, and hollyhock, taken 

 in the same conditions, present exactly the same mode of growth 

 and exfoliation of their cortical layer, with this exception only — 

 that the exfoliable layer of the radicle of the hollyhock is com- 

 paratively very abundant, rich in viscid matter, and the cells of 

 which it is composed more closely packed than those of wheat, 

 although loosely connected, in the manner of an epidermis, by 

 the interposed viscid substance. 



The radical extremities of wild chicory, of cultivated lettuce, 

 of Crepis virens, of Papaver somniferum, black mustard, and cul- 

 tivated Camelina, allowed to exfoliate in distilled water, gave 

 solutions which, on evaporation in vacuo, left residues scarcely 

 coloured, of a gummy aspect. Those obtained from the radicles 

 of chicory and Crepis virens exhaled a poisonous odour, and had 

 a bitter taste analogous to that of lactucarium. That furnished 

 by the radicles of poppy has the odour and taste of opium, and 

 those derived from black mustard and Camelina have a saline 

 sulphurous taste, and emit an unbearable alliaceous odour. 



These matters, which, in the ordinary course of vegetation, 

 are abandoned to the soil, seem to afford an explanation of the 

 antipathies of certain plants towards others, since direct expe- 

 riment has proved that they are always hurtful when they are 

 absorbed by the plants in sufficient quantity. 



That portion which, for the better comprehension of the 

 facts, we have called the axis of the radicle, presents greater 

 difficulties in its study, depending in part on the fact that its 

 summit is masked by the adhering cortical zone not yet ex- 

 foliated, and in part that some of the cells of this latter region are 

 loaded with very fine feculent granules, which interrupt the 

 passage of light. But by removing the point of the radicle to 

 the extent of about a quarter of a millimetre, and moistening 

 its apex with a drop of phosphoric acid diluted with twice its 

 weight of water, the still adherent cortical cells may be made to 

 exfoliate, and the extremity of the axis of the root is set free, 

 while the feculent granules of its cells are dissolved, and leave 

 the tissue conveniently transparent. 



