ORGANIC STRUCTURE. 91 



large fleshy roots of asparagus, (Fig-. 23,) and the 

 like. These are evidently preservative appendages 

 containing a store of nutriment for the use of that 

 part of the crown to which they are attached. In 

 fact they are only a modification of a tuber, but with 

 this difference they are destitute of buds or of any 

 principle of reproductive life, save that which they 

 possess as an appendage of the crown. 



The fibrous roots and stems of shrubs and trees 

 are increased in thickness together. Whilst the stem 

 is receiving a new layer of alburnum, the roots also 

 receive an addition of the same kind. It is from this 

 circumstance that roots are known to be more enlarged 

 toward autumn than at any other time of the year. 



Some practical men are of opinion that the princi- 

 pal office of the roots is only to fix the plant in the 

 earth. They infer this from observing that some 

 plants live entirely in air ; that in the order Pan- 

 danece and its alliances, the first roots only are pro- 

 duced from the collet, and all the subsequent ones 

 from the stem ; the roots of cuttings moreover are 

 produced by the stem, protuberances are formed 

 above^ wounds and ligatures; and there are many 

 instances of accretion or enlargement of the inferior 

 parts of plants, which is evidently received from the 

 influence or action of the organisation above. 



Admitting that these instances are corroborative, 

 to a certain extent, of the opinion above alluded to, 

 yet, from the ordinary and well-known functions of 

 the roots in supplying water and nutrition on all 

 occasions to the head, it is impossible we can con- 



