THE QUESTION OF ROOT EXCRETIONS 259 



Unger, and his pupil, Walser, showed that there had been certain 

 flaw? in the work of Macaire-Prinsep and made objections to his results. 

 Walser believed that, if Macaire's statements were correct, it would be 

 possible to demonstrate the presence of organic material in the soil 

 similar in composition to that existing within the plants which had 

 grown upon it. Braconnot, making the same assumption, attempted 

 to demonstrate the existence of opium-like bodies by washing the soil 

 on which plants of the poppy family had been grown for several years. 

 He obtained a solution of inorganic compounds, and, in addition, only 

 traces of organic compounds, and concluded that " If organic excre- 

 tions really take place in the natural state of the plant, they are, as 

 yet, so obscure and so little known as to justify the assumption that 

 some other explanation must be given for the general system of rota- 

 tion." Working without the proper idea of the difficulties of such a 

 task and without adequate knowledge of the organic compounds in the 

 soil, it is little wonder that they failed to demonstrate the presence 

 of compounds in the soil which might be regarded as excretory matter 

 from plants. They deserve credit, however, for showing that Brug- 

 mans had entirely misinterpreted the death of the root-hairs and the 

 decortication of the growing roots and had assumed that this material 

 was solid excretory matter from the living root. 



One of the most scientific attempts to study this question appears 

 to have been made by Alfred Clyde, the results of whose work were 

 published in 1846 in the Transactions of the Highland and Agricul- 

 tural Society of Scotland, and which won for the author a premium of 

 twenty sovereigns. His modus operandi was to raise plants in pots 

 of garden soil, sand, moss or charcoal; to remove them at different 

 times; carefully wash their roots free from all adherent material and 

 place the root systems in vessels of distilled water. After a certain 

 length of time had elapsed, the composition of the water in the various 

 vessels was studied. 



Mr. Gyde reported that the roots imparted to the water soluble 

 substances, to be regarded as excretory material, and that these excre- 

 tions seemed to be yielded in greater abundance by plants having coarse 

 roots like beans than by those which had finer roots, like wheat. In 

 some instances the water acquired an odor which was separable on the 

 application of heat and could be distilled over when the water was 

 placed in a retort. Plants like the bean and cabbage imparted an 

 odor to the water similar to that which characterizes their leaves. 

 Plants when in bloom were observed to emit more excretory material 

 than when young or when ripening their seed; but in any case the 

 amount of excretion obtained after evaporating the water was very 

 small. When this small amount of organic matter was reapplied to 

 the soil in which other plants were growing, no harmful effects were 



