Scrophulariaceae. 501 



walls which are quite thin in V. alpina, but of the same 

 thickness as in the other cells of the cortex in V. fruticans. 

 In the latter species there are distinct growth-zones in the 

 xylem-portions of the stele, whilst such growth-zones are 

 lacking in V. alpina. 



It is common to the roots of Eiiphrasia, Bartschia and 

 the Pedicularis spp. to have the primary cortex few-layered 

 and its cells frequently very thin-walled; root-hairs are 

 usually wanting (in some specimens of Euphrasia arctica, 

 alone, I found a few scattered root-hairs). 



In the species of Euphrasia the epidermis persists a long 

 time; according to Hovelacque the same is the case in 

 Bartschia, but in this I found that it may sometimes die 

 away early. With the exception of P. Sceptriim carolinum 

 it dies away very quickly in the Pedicularis spp. which have 

 been investigated ; even in roots a millimetre thick, I found 

 the cells collapsed and partly thrust off; the outer walls of 

 the layer below the epidermis become cuticularised, and 

 where the grow^h in thickness of the root is considerable 

 (P. euphrasioides, hirsuta, lanata, flammea and Oederi) the 

 cells of the exodermis as well as of the other 3 — 6 layers 

 of the primary cortex become greatly elongated tangentially 

 and divided by thin radial walls. 



The primary cortex persists a long time. 



In Bartschia alpina and P. capitata a cuticularised 

 lamella arises in the wall of the endodermal cells, in the 

 former species all the way round, in the latter only in the 

 inner and radial walls. 



The Casparian dots were very distinctly discernable in 

 Euphrasia arctica, and in P. lapponica, whilst they were 

 quite faint in P. hirsuta and lanata. 



Lacunæ, such as are found, for instance, in the primary 

 cortex in P. palustris (Hovelacque), were, in the species 



