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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
liave wandered by a river’s bank, as also the net work formed 
around any food-yielding substance, such as a piece of leather 
or of bone as above alluded to. 
With reference to the varying degrees of development of the 
roots according to the nature of the soil they traverse, the 
following extract from Knight’s ‘‘Horticultural Papers” may 
appropriately be cited :— 
“ A trench which was twenty feet long, six wide, and about 
two deep, was prepared in my garden, in the bottom of which 
trench was placed a layer, about six inches deep, of very rich 
mould, incorporated with much fresh vegetable matter. This 
was covered, eighteen inches deep, with light and poor loam, 
and upon the bed thus formed, seeds of the common Carrot 
(Daucus Carota) and Parsnip (Pastinaca sativa) 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 soil 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 considerable 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.”— Knight’s 
“ Horticultural Papers ,” XII., On the Origin and Formation of 
Foots , p. 159. 
The most accurate investigations, however, as to the effect of 
the medium in which they are growing, on the production of 
root fibrils, are those of Nobbe, summarised in “ How Crops 
Grow,” (English Edition, p. 231). It is there shown, as a 
result of well devised experiments, that where the fertilising 
material was thoroughly mixed with the soil, the root-fibrils 
were evenly dispersed throughout, but where the fertiliser 
