Vegetable Excretions of Plants. 279 



pots bear fruit for several years, without the soil they grew in 

 being changed. Leguminous plants are supposed to possess 

 the excreting faculty in an eminent degree; but plants of this 

 tribe do not readily poison themselves ; for I have known the 

 common kidneybean grown on the same plot of ground for at 

 least ten successive years, and that, too, without any diminution 

 of luxuriance or productiveness. Even the strawberry plant, 

 with which it is recommended to make experiments, in order ta 

 confirm the theory, on account of its " deposition of excre- 

 mentitious matter," is frequently, in ill-managed gardens, suf- 

 fered to occupy the same beds for a long series of years. Of 

 course, after a certain period, its fertility diminishes with its age; 

 but there is no evidence to prove that this barrenness arises from 

 " specific poisoning of the soil." It would be quite as reason- 

 able to ascribe the decrease of fertility to want of food, and to 

 the crowded state of the bed not allowing the young plants pro- 

 perly to develope themselves. I could mention many other 

 cases in point; but these are sufficient to show that there are at 

 least some plants not guilty o^felo de se ; and, if this faecal pro- 

 perty is not universal in the vegetable kingdom, but confined to 

 part only of its members, can it justly be made the foundation of 

 a general theory in horticulture ? 



The discoverers (for there seem to be several who claim the 

 merit) of this additional function of roots do not explain the 

 manner in which it is effected. Do the spongioles indiscrimi- 

 nately suck up every thing presented to them, if sufficiently 

 fluid to pass through their pores, and then, by a sort of elective 

 power, with which their interior only is endowed, do they turn 

 back all that is hurtful or useless, and allow the convertible 

 matter alone to proceed on its course? or do the good and evil 

 principles travel in company through all the various turnings 

 and windings of the plant, until they are finally separated in 

 the leaves, whence the refuse must again be consigned to the 

 roots to be ejected at their leisure ? Again, is the excrement 

 voided by the spongioles alone, or do the whole of the roots 

 possess that property? If the former, is there another instance 

 in nature of one simple organ performing, at the same time, two 

 functions so diametrically opposed as absorption and excretion ? 



These objections to the faecal theory appear to me sufficiently 

 weighty to suspend its admission into works on horticulture, as 

 an established doctrine, until it has been further corroborated by 

 diversified experiments. Those of M. Macaire, as quoted by 

 G. J. T. (Vol. X. p. 12.), are by no means conclusive ; on the con- 

 trary, those made with the bean plants might with equal pro- 

 priety be adduced as an argument that exhaustion of the peculiar 

 nutritive matter required by the bean, and not poisoning of the 

 water, was the reason why the second plant did not thrive. If 



X 4 



