98 ANATOMY AND PHYSIOLOGY OF 



tions liad passed, plants of the same species would not flourish, 

 while other species conld absorb it with impunity. From these 

 experiments, De Oandolle drew the conclusion that these excre- 

 tions were to be compared with the urinary excretions of ani- 

 mals, and explained from the doctrine, that no organized being 

 could use its own excrement for food, the fact of experience, that 

 cultivated plants, the Cerealia for example, would not flouiish for 

 any long uninterrupted period upon the same soil. 



The repetition of these experiments by others, left no doubt 

 that Macaire had not gone to work with the requisite circumspec- 

 tion in making them, Braconnot (" Ann, d. Chimie. et d Physf' 

 torn. Ixxii.p. 32) shewed that milk-sap was effused into water from 

 the roots of plants of Lactwoa which had been dug out of earth, 

 partly in consequence of laceration, partly in consequence of 

 irritation; buit that earth wherein Neriiim, JEtq^horhia^ Asclepias, 

 and Papaver^ had grown, some of them for a series of years, was 

 totally devoid of such excreted matters, and that merely traces 

 of organic substances, neither bitter nor acrid, were met with in 

 it, and these he attributed to the decomposition of the rootlets. 

 The experiments of Walser ("Unters, UK d, WuT^elausscheiduti- 

 gen" Dissert. Tubingen, 18S8) likewise gave a completely negative 

 result, as did also Boussingault's (^^Ann. d. Ohim. et d. Physf' 1841, 

 torn, i,, 217). Moreover that the noxious salts absorbed are not 

 excreted by uninjured roots, but only extracted by the water from 

 injured roots, was shewn by the experiments of linger ( " Ueb. 

 d. Vegetat v. KitzbuheV 149), and Meyen (^^Pliysiologf' ii. 530), 

 on Lemnaj and Braconnot demonstrated that Macaire had made 

 a clumsy mistake in his expeiiments, to prove the excretion of 

 an absorbed salt of lead, since he overlooked that the close 

 bundles of roots carried the solution of the lead salt over, into the 

 vessel of water into which another portion of the roots of the 

 same plant dipped, by capillary attraction. 



Under these circumstances, we must regard the secretion of an 

 excrementitious fluid by the roots as not proven. At the same 

 timej it is certainly no evidence that the roots do not excrete at 

 all. I lay no weight upon the reason mentioned by Schleiden, 

 that the endosmose of the roots must be accompanied by an 

 exosmose, for it is too hazardous to deduce the existence of a 

 second phenomenon from one of which so little is known in regard 

 to the forces active in it, as is the case of the absorption of the 

 roots. A few other circumstances perhaps speak in favour of it. 

 Many experiments shew that the roots of living plants exert a 

 chemical influence upon organic substances placed in contact with 

 their roots. Trinchinetti (^^svM.fac, absorh d. radioi." 57) observed, 

 that a decoction of humus underwent foetid putrefaction when 

 left to itself, but this did not take place when the roots of living 

 plants were placed in it. In many cases it is observed that the 

 roots exercise a solvent action upon solid organic substances; thus 



