1839] 



FARMERS' REGISTER 



463 



atmosphere, readily taking fire when a flame is 

 brouijiu in contact willi it, and burning without 

 doing any injury to the plant,"' 



Tlie othce of excreting such matter as is ibund 

 unsuitable lor the nourishment of a plant is not 

 confined to the stem and leaves but is in fjict per- 

 formed by the root to a much greater extent than 

 by any other organ. That roots in some cases give 

 oti'a peculiar nmiter,ha3 been known for a long time; 

 but it is only within the present century that this 

 has been admitted to be a tunction common to all 

 roots. As has been already remarked, the pos- 

 session of the power of rejecting such matter as is 

 found unsuitable tor their nourishment, would seem 

 (o be a necessary condition of the lile of plants; 

 did they not possess it, their vessels must soon be- 

 come clogged, and rendered unfit (or performing 

 their appropriate office. From some experiments 

 which have been performed, it would seem that 

 plants possess the power of disembarrassing them- 

 selves of all kinds of matter which are Ibund unfit 

 for their nourishment. JMacaire took a plant of 

 mercury (^mercurialis annua) and having divided 

 its roots into two parcels, introduced one ol them 

 into a glass containing a week solution of acetate 

 of lead, and the other into a glass of pure water. 

 At the end of a few hours he found that the glass 

 of pure water had become perceptibly tinged with 

 acetate of lead, which of course must have been 

 taken into the circulation by the roots on one side 

 of the plants, and thrown of! again by the roots 

 on the other. In this instance the excreted matter 

 was thrown back without having undergone any 

 change ; as a general thing, however, this is not 

 the case ; thus, leguminous plants, of which the 

 pea may he mentioned as an axample, although 

 they absorb only carbonic acid and water, will 

 excrete the elements of those substances combined 

 so as to form a species of gum. Grasses excrete 

 principally certain alkaline and earthy muriates, 

 and carbonates, but very little of any gum ; pa- 

 paveraceous plants excrete a bitter matter anal- 

 ogous to opium ; euphorbias a gum-resin of a 

 yellowish white color, and an acid flavor. 



From observation, we learn that tiie matter ex- 

 creted by plants is, as a general thing, thrown out 

 in such a condition as to be, not only unfit: again to 

 enter the system of the plant rejecting it, but po- 

 sitively deleterious ; and luriher, that the excre- 

 tions of difi'erent plants dilfer so much Irom each 

 other, that whilst that thrown out by a plant is 

 deleterious to others of the same species, it is 

 sometimes well adapted to the nourishment of 

 those of a difierent species. This fact will explain 

 some of those rules which experience has taught 

 the practical agriculturist. For instance, the rule 

 that the same crop should not he grown for sever; ! 

 years in succession upon the same piece of ground. 

 It will not do to say, as is often done, that a second 

 crop of wheat will not grow as well upon any- 

 given spot, as the first, because that spot has been 

 exhausted of too great a portion of its nutritive 

 matter by the first. This it is true is one reason, but 

 if it be the only reason, or even the principal rea- 

 son, we may ask, how is it that a crop of corn will 

 succeed almost as well as if the wheat had never 

 been grown there? The true explanation seems to 

 be that the failureof the second crop of wheat arises 

 not so much from the exhaustion of (he soil, as from 

 the existence in the soil of a portion of matter po- 

 sitively deleterious to wheat, deposited by the fi st 



crop; at the same time this matter is not injurious to 

 the corn, and hence that crop will succeed when 

 wheat would I ail. To grow the same crop for 

 several successive years upon the same spot, is, as 

 De Candolle has very pertinently, though perhaps 

 not very elegantly remarked, "like liiediiig an 

 animal upon its own excrements." It is much to 

 be desired thai this matter should be made a sub- 

 ject of more careful and more accurate experiments 

 than it ever has as yet, as it is one which would 

 doubtless admit of very important practical appli- 

 cations. If the precise nature of the matter retained 

 and of that rejected by each of the crops in com- 

 mon cultivation could once be ascertained, it would 

 seem to be an easy matter to determine the best 

 order in which those crops should succeed each 

 other. Perhaps too if this subject was better un- 

 derstood, we should find that the way in which 

 some manures benefit land, is not by supplying 

 nourishment to the plants growing on it, but by 

 removing this deleterious matter from their mots. 

 If this matter possessed the character oi' an acid 

 (and there are several facts which seem to render 

 it almost certain that such is the character of the 

 matter excreted by many plants) lime would act 

 in this way ; being a salafiable base it would 

 unite with the acid and neutralize its properties. 

 The rotation of crops is a matter very generallj' 

 attended to in farming, but in gardening, where it 

 is of still greater importance, itisfi-equently neglect- 

 ed; and as a necessary consequence, garden plants 

 degenerate under so injudicious a system of cul- 

 tivation. Our best gardeners have been taught 

 by experience never to sow the same plant even 

 tor two years in succession upon the same spot of 

 ground. 



When the root of a plant is cut off, and the 

 stem placed in water, the excrementiiious matter 

 which in other circumstances would have been 

 discharged irom the roots, issues from the end of 

 the stem. Hence it is that water in which flow- 

 ers have been kept for some time, ahvaj's be- 

 comes offensive. We commonly say that the 

 water has become putrid; but pure water can never 

 become putrid, the offensive character of the 

 water in such circumstances arises entirely from 

 the rejected matter excreted by the stem. It is a 

 fact, which I suppose all must have noticed, that 

 some plants when placed in water together seem 

 to keep each other alive, whilst others produce just 

 the opposite eft'ecf. This is owing to the naiure of 

 ihe matter excreted by their stems. Where the 

 matier rejected by one plant is of such a nature as 

 to be suited to the nourishment of the other, they 

 will keep each other alive; but where the opposite 

 ':^ I lie case, they will hasten each others death. In 

 :':e same way we explain the fact that a nosegay 

 composed of many different flowers, will, when 

 placed in water, generally preserve its freshness 

 much longer than one composed of the same num- 

 ber Ol' flowers of the same species. There is a class 

 jf plants commonly called weeds which cannot 

 grow in the immediate neighborhood of our com- 

 mon cultivated plants without materiall}'- injuring 

 them. This is doubtless in part owing to their con- 

 suming the nutritive matter contained by the soil, 

 and in part also to their overshadowing the culti- 

 vated plant and thus shutting it out from the direct 

 action of the sun, but it is also in part owing to the 

 nature oi'ihe matter which they deposite in the soil. 

 The common opinion that weeds poison the plants 



