163 



BOTANY. 



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

 soon hecomes transformed into the cortical portion of the 

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

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

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

 generating tissue of the root-cap. 



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

 shown than in the previous figure. The central plerome 

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



Pig. 138. — Median longitadinal section of the apex of the root of the buckwheat 

 {Fagopyrum esculentum). pc, pericamblum, constituting the boundary of the plerome 

 column ; e, dermatogen ; between e and^c, peribleni ; A, root-cap. — After I)e 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 (A) 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 



* Another ofHanstein'a terms, from the Greek ncplSXrifia, a cirak. 



