THE ROOT. 



f)7 



meets the stem, is called the collum ; the remote, opposite ex- 

 tremities, the ends of the fibres, being chiefly active in absorp- 

 tion, are the spongioles. Neither of these 

 terms denotes distinct organs, but places 

 only, and are often convenient. The fi- 

 brils , or fibrillce, are those minute hairs 

 (seen only with a lens) which clothe the 

 younger fibres. They arise from the 

 tender epidermis or skin, and perish when 

 that thickens into bark. These are the 

 efficient absorbers of liquid nourishment. 

 They are developed and perish annually 

 with the leaves, whose servants they are. 

 Few of them remain after the fall of the 

 leaf. This fact plainly indicates that the 

 proper time for transplanting trees or 

 shrubs is the late Autumn, Winter, or se, Extremity of a rootlet of su. 



ic.. . . -if P le > witl1 its Hbrilla and ipougioln 



early Spring, when there are but few (> magnified so diameters. 

 tender fibrillse to be injured. 



200. Two modes of root-development are definitely distin- 

 guished. First, the AXIAL MODE is that where the primary, 

 simple radicle, in growing, extends itself downward in a main 

 body more or less branched, continuous with the stem, and 

 forms the permanent root of the plant. Such is the case with 

 the Maple, Mustard, Beet, and most of the Dicotyledonous 

 Plants ( 183). 



201. Secondly, the INAXIAL development is that where the 

 primary radicle proves abortive, never developing into an axial 

 root; but, growing laterally only, it sends out little shoots from 

 its sides, which grow into long, slender roots, nearly equal in 

 value, none of th^m continuous with the stem. Of this nature 

 are the roots of all the Grasses, the Lilies, and the Monocotyle- 

 dons generally, and of the Cryptogamia. Plants raised from 

 layers, cuttings, tubers, and slips are necessarily destitute of 

 the axial root. 



202. The various forms of the root are naturally and 

 conveniently referred to these two modes of development. The 

 principal axial forms are the ramous, fusiform, napiform, and con- 



