42 FOEMS OF ROOTS. 



root), by Eichard. In their after progress these roots follow the 

 arrangement seen in the woody part of the stein. In some cases, as 

 in the Walnut and Horse-chestnut, there is a prolongation of the pith 

 into the root to a certain extent. 



In Monocotyledonous plants the young root or radicle pierces the 

 lower part of the axis (fig. 105 r), is covered with a cellular sheath, c; 

 numerous fibrUs, / r' / /, are then developed like adventitious 

 roots. These plants are therefore called by Eichard, Endorhizal 

 hvdov, within) ; and the sheath is denominated Goleorhiza {xoXehe, a 

 sheath). In their after progress they usually retain their compound 

 character, consistmg of fibrils, most of which often remain unbranched 

 (figs. 100, 101). The first-formed roots which surround the axis, 

 if the plant is perennial, gradually die, and others are produced in 



Fig. 106. 



succession farther from the central axis. In Endogenous roots, the 

 same structure is observed as in the stem. Thus, fig. 106 represents a 

 section of a root of a Palm, composed of cellular tissue, porous vessels, 

 V p, modified spiral vessels, v s, fibrous or woody tissue, /, and latici- 

 ferous vessels, I. Eoots are pushed out from various parts of the 

 stems of many Palms, and are applied closely to the surface of the 

 stem. 



Fig. 105. Grain of wheat germinating, g, The nia38 of the grain, t, The young stem begin- 

 ning to shoot upwards, r. The principal root from the axis. Lateral roots, / / r* /, covered, 

 like the preceding, with small hairs or threads. Coleorhiza or sheath, c c c, with which each 

 of the roots is covered at its base, while piercing the superficial layer of the embryo. Fig. 

 106. Transverse section of part of the root of a Palm {Dvplothemivm vuiriHtnum), to show 

 the mode in which the cells and vessels are arranged, v p, Large porous vessels situated in 

 the interior, v s, Scalarifonn or modified spiral vessels more external, and becoming smaller 

 the farther they are from the centre. /, Fibrous tissue, or elongated cells, accompany- 

 ing the vessels. I, Groups of laticiferous vessels of different sizes, the larger being inside. 



