THE VEGETABLE CELL. 97 



A. innocun These objections are motj it is true, by Scliultz witli tbe asser- 

 tion tliat tbe milk-saps of Euiyhorhia, &c , are not poisonous, but that the 

 poisonous matter comes from reservoirs of secretion wouiidetl ai the same 

 time as the milk-vessels ; this, however, is a complete flight of imagina- 

 tion, for which not the shadow of a proof exists. 



So the whole of Schultz's theory of the milk-sap is a tissue of the most 

 unfounded hypotheses/ offering the most glaring contradiction to positive 

 facts. 



Though the physiological import of the secreted fluids preserved 

 in the interior of plants is uncertain, there is no doubt that the 

 purpose of those secretions which occur upon the surface of plants 

 might be more readily made out, if the fluids were excreted in suf- 

 ficient quantity to be collected. Whether siicli excretions occur, is 

 still unknown. Here, of course, we can merely have to do with 

 those secretions which have a more general diffusion, since local 

 exudations, which only occur in particular plants, like the acids in 

 the glandular hairs of Gioer arietinuTn, the gummy seci-etions of 

 Primulm, Sllenem, &c , can merely serve special purposes. 



Such a secretion has been attributed by many to the root, 

 especially by Brugmans ("Da mutata huwhoruTYi in regno organieo 

 indole,'' Ludg Batav. 1789. — Up to the time of Schleiden, a 

 number of authors have cited under this head a treatise by 

 Brugmans, "De Lolio ejusdemque varia specie/' but this essay 

 seems to have no existence), who thought he discovered that cei^- 

 tain plants do not flourish in the vicinity of certain others, e. g,, 

 Avena near Gardiiiis arvensis, wheat near EHgeron acre, flax 

 near JSuphorbia Peplws and Scabiosa arvensis^ &c. He ascribed 

 this to the excretion of a watery fluid from the roots of the 

 weeds, having the power of corroding the roots of the cultivated 

 plants. These excretions were considered by others, for example 

 by Plenk (^'^Phydolog" 43), Humboldt (^^ Aphorism, a. d. chemisch 

 Physiol, d. Pflanzen/' 116). Cotta (^^Naturhet ub. Bewegung c?. 

 Safis" 49), as evacuation of excrements, and the utility of fallows 

 was deduced from the hypothesis that the excrements must be 

 allowed to decompose in the soil before other plants could flourish 

 in it. But this excretion from the roots was denied by others, e. g., 

 Hedwig, and generally, speaking, no very great value was at- 

 tached to it. The attention of physiologists was drawn again to 

 the matter by Macaire Prinsep instituting, at De CandoUe's sug- 

 gestion ("if/m de la Soc. de Phys. de Qenive/' v. 287), experiments 

 which appeared to give positive results. Macaire found, namely, 

 that plants which had their roots carefully dug up and placed in 

 water, gave out into this, chiefly during the liight, organic mat- 

 ters, which differed according to the kind of plaut, being opium- 

 like from the Laetucece and the Poppy, acrid from Eup>hoThha^ 

 mucilaginous from the Legwminosw, &c. At the same time, he be- 

 lieved that he found acetate of lead taken up by the plant, again 

 excreted in this way, further, that in water whereinto these secro- 



u 



