OF THE GROWTH OF ROOTS. 15,9 



light and poor loam, and upon the bed thus formed, seeds of the common 

 carrot (Daucus carota) and parsnep (Pastinaca satlva) were sowed. 

 The plants grew feebly till near the end of the summer, when they 

 assumed a very luxuriant growth, grew .rapidly till late in the autumn, 

 and till their leaves were injured by frost. The roots were then 

 examined, and were found of an extraordinary length, and in form 

 almost perfectly cylindrical, having scarcely emitted any lateral fibrous 

 roots into the poor soil, whilst the rich mould beneath was filled with 

 them. 



In another experiment of the same season, the preceding process was 

 reversed, the rich soil being placed upon the surface, and the poor 

 beneath. The plants here grew very luxuriantly, and acquired a consider- 

 able size early in the summer ; and when the roots were taken up in the 

 autumn, they were found to have assumed very different forms. The 

 greater part had divided into two or more unequal ramifications, 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 placed 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 of 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 I think it necessary to describe it very minutely. 

 Some seeds of the common bean (Vicia 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 whatever position the pots might 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 depressed into the mould as to be about half covered : by 

 which means each radicle, when first emitted, was in contact with the 

 mould above, and the air below. Water was then introduced through 



* See above, No. VII. 



