163 



BOTANT. 



137, m, f, g), which is ensheathed by the Perillem,* which 

 soon becomes transformed into the cortical portion of the 

 <root {x, r, Fig. 137). The epidermis is developed from the 

 Tegion from which the root-cap grows, and, in fact, as will 

 be shown below, it is a continuation and modificaLion of the 

 generating tissue of the root-cap. 



210. — In Fig. 138 the relation of the parts is even better 

 :shown than it .he previous figure. The central plerome 

 -column is surrounded by a layer of active cells, the pericam- 



fig. 138.— Median longitudinal section of the apex of tlie root of the huckwheat 

 '{Fagopyrum eseulenfum), pc^ pericamhlum, constituting the boundary of the plerome 

 column ; e, dermatogen ; between e andpc, periblem ; 7i, root-cap. — Alter De Bary. 



bium (pc) ; outside of the latter lies the periblem, or young 

 cortical portion, and still outside of this the dermatogen 

 (e), which further back on the root becomes the epidermis. 

 The root-cap {h) lies entirely outside of, and is quite distinct 

 from, the back portions of the dermatogen, but near the 

 apex of the root there is a tract in which dermatogen and 

 root-cap apparently fuse into one. At this point the layers 



* Anotber of Haustein's terms, from tlie Greek neplBWinm. a cloak. 



