4'22 On the Causes which iiifluence 



luxuriantly, and acquired a considerable size early in the 

 summer ; and when the roots were taken tip in the autumn, 

 they were found to have assumed very different forms. The 

 greater part had divided into two or more unequal ramifi- 

 cations, very near the surface of the ground, and those 

 which were not thus divided tapered rapidly to a point at 

 the surface of the poor soil, into which few of their fibrous 

 roots had entered. , 



In other experiments, seeds of almost all the common 

 esculent plants of a garden were so pliced that the young 

 plants had an opportunity of selecting either rich or poor 

 soil ; which was disposed, in almost every possible way, 

 within their reach ; and I always found abundant fibrous 

 roots in the rich soil, and comparatively few in the poor. 



The following experiment afforded the most remarkable 

 result, and one the least favourable to the hypothesis which 

 I have advanced in a former paper*, and to the conclusion 

 which I shall now endeavour to support ; and therefore \ 

 think it necessary to describe it very minutely. Scmie seeds 

 of the common bean {Vic'ia faba), the plant with which 

 many former experiments were made, were placed upon the 

 surface of the mould in garden pots, in rows which were 

 about four inches distant from each other. A grate, formed 

 of slender bars of wood, was then adapted to the surface of 

 each pot, so as to prevent both the mould and the seeds 

 falling out, in wliatever position the pots nn'ght be placed ; 

 and the bars were so disposed, as not at all to interfere with 

 the radicles of the seeds, when protruding. The pots were 

 then directly inverted; and the seeds were consequently 

 placed beneath the mould ; but each seed was so far de- 

 pressed into the mould, as to be about half covered : by 

 which means each radicle, when first emitted, was in con- 

 tact with the mould above, and the air below. Water was 

 then introduced through the bottom of the inverted pot, in 

 sufficient quantity lo keep the mould moderately moist ; 

 and the pots being suspended from the roof of a forcing 

 house, the seeds soon vegetated. 



In former expeiimentsf, wherever the seeds were placed 

 to ve2Ctaie at rest, the radicles descended perpendicularly 

 downwards, in whatever direction they were first protruded ; 

 but under the preceding circumstances tliey extended hori- 

 zontally along the surface of the mould, and in contact 

 with it 5 and in a few days emitted many fibrous roots up- 

 wards into it: just as they would have done, if guided by 



* Phil. Trans. ISOG, page 1. f 'bid. 



the 



