General Notices. 221 



animals and plants perform on the grand system of nature's working, but it 

 explains in a satisfactory manner the ground of the mistake into which those 

 have fallen who suppose that plants, in the course of their natural operations, 

 give out to the soil a certain matter, which is a poison to succeeding plants 

 of the same species. It is not any thing given out by the living and healthy 

 which has this effect ; it is the decomposition, or rather the putrefying decay, 

 of that which has performed its functions, and requires to be converted into 

 elementary matter, before it is again available for the vegetation of the same 

 species." 



This being a new explanation of the reason why the same species of plants 

 do not succeed, if repeatedly sown or planted on the same spot, is at least 

 curious. It is very different from the hypothesis of Professor DeCandolle, 

 and others, relative to the same circumstance. The professor thinks that 

 the roots of plants have excretory pores or ducts, by which they can reject 

 facal matter from the system, and that it is this ejected matter which acts as 

 a poison, or at least as unpalatable food, to succeeding plants of the same 

 kind. From the experiments of M. Macaire, it appears certain that plants 

 do discharge coloured fluids into pure water, which they had imbibed in a 

 prepared fluid, in which they had been previously placed : thus showing that 

 the roots can emit as well as absorb fluids ; but whether these rejectments 

 be faeces, or poisonous to other plants, is still far from certain. 



Mr. Mudie, reasoning from analogy, asserts that living vegetation emits 

 nothing deleterious ; but parts of vegetables destitute of life, and in a 

 state of putridity, he believes to be highly offensive to living plants of the 

 same kind, and states this to be the true reason why a change of crops is 

 necessary. 



We have no practice, either in the garden or field, which bears upon these 

 ideas, so as to furnish direct proof of their validity, or the contrary. In the fields 

 we cultivate green crops to be ploughed down as manure ; but this is for the 

 service of a white crop. Brank or coleseed is sometimes ploughed into a 

 fallow intended for wheat, and frost-bitten and rotten turnips are ploughed 

 in as a dress for barley and clover, and these succeeding crops are benefited 

 by having to live upon the moisture and putrid remains of the interred plants. 

 But in these cases the living and the dead are not congenerous ; and, there- 

 fore, their union does not invalidate Mr. Mudie's opinion. In the garden we 

 are constantly burying weeds, without observing them to grow the worse for 

 being obliged to batten on their own ancestry ; but here, indeed, where so 

 much art is had recourse to, the affections of useless plants pass unnoticed. 



Mr. Mudie enters deeply into the organisation of every living thing, and 

 repudiates the idea, that plants or parts of plants can acquire organisation 

 fortuitously. On this subject he is rather severe on some of our professors 

 of botanical and other sciences. He declares that "mechanical and chemical 

 actions, and also the passing of the one into the other, we can understand ; 

 and the knowledge which we obtain of them from our own experiments is exceed- 

 ingly useful, as applied to explain the phenomena and the action of all those 

 parts of nature which are not connected with life, either animal or vegetable : 

 but, when we come to consider the relation between action in dead matter, 

 and any of the actions of life, we find ourselves beset by difficulties which 

 we cannot overcome ; because the transition of any portion of matter from 

 the dead to the living, or from the living to the dead, whether the living state 

 be that of animal or of vegetable, is a mystery beyond the limits of our 

 ordinary philosophy. Some have, indeed, stumbled upon what they supposed 

 to be the steps of the transition here, or at least a vague sort of approxi- 

 mation to them ; and we have had, and have at the present day, men seated 

 in professional chairs, authorised and appointed for the instruction of the 

 young and the ignorant, and guarded against public enquiry by doctorial and. 

 other dubbings, who, in violence of logic and common sense, and outraging 

 even the shadow of philosophy, speak of " organic matter waiting to be 

 organised," and so docile withal in its nature that it is more plastic than 



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