VB( STRUCTURE AND FUNCTIONS 



ley, oats, &c., but when the crown, from any 

 cause, such as the soil, climate, or culture, is 

 rendered strong, such annuals are brought to 

 grow two years and then are called biennials, 

 or for a succession of years and then are called 

 perennials. 



The fibres, though an essential part of each 

 root, may be removed in most cases without in- 

 jury to the plant, provided the crown is suf- 

 ficiently healthy and vigorous to push out new 

 ones. It is at the tips of these fibres that the 

 spongelets are placed, which absorb the pabu- 

 lum from the soil, and in the event of the 

 spongelet being removed by any cause from the 

 point of the fibre, two lateral shoots imme- 

 diately are thrown out, (provided the plant is 

 sufficiently vigorous to bear the temporary loss 

 it thus sustains,) each provided with its sponge- 

 let, and thus the destruction of the one becomes 

 a source of strength to the plant. It was on 

 this principle that TuU's famous horse-hoeing 

 husbandry was founded: "that by ploughing 

 between the rows of wheat, and thereby cutting 

 off the tips of the fibres, that for every sponge- 

 let thus destroyed two were reproduced by the 

 plant, thus giving the plant two spongelets 

 where one had previously existed." There 

 were other collateral benefits to be derived from 

 this method, but the one in question was one of 

 the principal. 



That plants have the power of accommo- 

 dating themselves to circumstances is proved 

 in a most beautiful manner from the fact, that 

 when planted in a dry and arid soil an infi- 



