38 



STEUCTDEE OF BOOTS. 



Pyrus japonica, and especially Anemone japoniea, have a power of 

 forming buds on their roots. The last-mentioned plant develops 

 these buds on every part of its extensively ramiiying roots, which 

 may be chopped into numerous pieces, each capable of giving rise to a 

 new plant. Such is also the case with the annulated root of Ipecacuan. 

 The part where the stem and root unite is the collwm, or neclt. In 

 woody plants, the fibres of the stem descend into the roots, and there 

 is an internal arrangement of woody layers, similar to that seen in 

 the stem itself. 



Roots are usually subterranean and colourless. Externally, they 

 have a cellular epidermal covering of a delicate texture, sometimes called 

 epiblema (p. 26), in which no stomata exist. Their internal structure 

 consists partly of cells, and partly of vascular bimdles, in which there 

 are no vessels with fibres which can be unrolled. Roots do not ex- 

 hibit true pith, nor a medullary sheath. The axis of the root gives 

 off branches which divide into radicles or fibrils (fig. 96), the ex- 



Pig. 96. 



Fig, 97. 



tremities of which are composed of delicate cellular tissue, and have 

 been erroneously called spongioles or spongelets. They are not separate 

 organs, and have nothing of the character of a sponge. Over these 

 root extremities a very thin layer of cells is extended, caUed a 

 PUeorhiza {■^TXog, a cap, and j/^a, a root). This sometimes becomes 

 thickened, and separates in the form of a cup, as in Screw-pines (fig 

 98), and m Lycopodia (fig. 1 38). Occasionally the extremities of roots 

 are enclosed m a sheath, or ampulla, as in Lemna. Cellular papUte 



Pig. 96. Tapering root of Malva rotundifolia, giving off teanohes and fibrils Fie 97 

 Toung root of Madder, showing cellnlar processes, h h h, equivalent to liairs. c. Outer 

 cells of the root not elongated into hairs. 



