THE ROOTS 



the vascular cylinder retains its freshness, even in the case of the delicate 

 seminal rootlets, during almost the whole life of the plant. 



In roots from which the cortex has decayed, the endodermis, pericycle, 

 and conjunctive parenchyma of the stele becomes very strongly sclerotic, 

 but the cells of the bast and the 

 xylem vessels preserve their normal 

 character (Fig. 29). 



The anatomy of the stronger 

 adventitious roots which spring 

 from the nodes of the stems at or 

 just above the surface of the soil 

 differs in certain points from that 

 of the seminal or thinner adven- 

 titious roots. The exodermis is 

 often more persistent, and immc- 



diatelv within it there is frequently 



"* 3 



developed a zone of sclcrotised 



cortical cells two or three cells thick (Fig. 30), which, for a time, protects 



. 



Fie. 29. Trans vcnc tcction of a portion of 

 dw vMcukr cytimkr of an old seminal root 

 ***"* M> < * 260) r .Cortex ; -. 

 endodernm; />. pericycle; /, phloem 



I i'. 30. Transverse section of a portion of an ndvrnfitiou* root from the ntxir imme- 

 diately above ihe toil turface ( 150). rv, Kxodcrnm ; A, (hick-walled cortical cell* ; r. 



thiit-vtallexi loriu.il icIU cunuinint; *.hloroplat* ; e, rndodrrtiul cell \vith thick mm r 

 wall ; r , (hm-\\.tllrvl cndtxirrnijl cell ; J. liynifird pericycle. 



the turgid cortex within from collapsing. In the cells of the thin-walled 

 cortical parenchyma of the stout adventitious roots arising from nodes just 

 above the soil surface, numerous chloroplasts are found, especially in the 

 inner layers, the central cylinder then appearing to be surrounded by a 

 zone of green tissue. 



