LECT. VIII.] STRUCTURE OF LIGNEOUS ROOTS. 409 



much thicker than that of any part above the soil. 

 The vessels are so arranged as to give a radiated 

 appearance to a transverse section, and I have 

 been able to trace the presence of divergent rays ; 

 but I am doubtful whether these are always present 

 in the smaller radicles. In the Vine we sometimes 

 find the bark running inwards, and dividing the 

 vessels into distinct wedge-like bundles (see Plate 

 7, fig. 11. *) ; and this may be the case, also, in 

 other radicles, to supply the place of other diver- 

 gent layers. 



The radicles given off from the caudex appear 

 to proceed from the medullary sheath and the first 

 ligneous layer ; and, - like the branches above 

 ground, originate in the first year's growth of 

 each additional length of the root, for they can 

 be traced to the medullary sheath in the thickest 

 caudex. When, however, they are given off from a 

 stem or a branch which has been laid down in the 

 ground, they originate in the alburnum of that 

 season (see Plate 6, fig. 9 -}-) ; and this is also the 



*In this figure, a. marks the pith in the slice of a shoot which 

 had been laid down and had rooted ; It. the first year's wood ; 

 c. that of the present year whence the radicle e. has shot forth ; 

 and d. the bark, the cuticle of which is seen uniting with that 

 of the radicle. 



f In this figure, which displays the transverse slice of a 

 Vine radicle magnified 750 times, a. marks the cuticle and the 

 parenchyma of the bark ; b. the divided orifices of the proper 

 vessels of the bark ; and c. those of the ligneous vessels. 



