504 Fr. J. Mathiesen. 



pallida (the increment was small and irregular) and some- 

 times in Bartschia; the runner-like portions of the shoots in 

 P. lapponica occasionally show two annual rings; in the 

 rhizomes in P. Sceptrum carolinum the xylem of the vascular 

 bundles always showed two growth-layers, since in the 

 second year of the rhizome-portion a group of vessels (and 

 stereom) is developed outside that produced in the first 

 year; the two groups are distinctly separated, some layers 

 of thin-walled unlignified parenchyma being found between 

 them. Thin-walled and unlignified cells are also present in 

 the Veronica spp. at the boundary between the annual rings. 



Cork-development occurs sub-epidermally in Veronica 

 fruticans in the basal, persistent portions of the shoots, and 

 in P. Sceptrum and capitata further within the primary 

 cortex; the cork is always only few-layered, but P. Sceptrum 

 carolinum develops, in addition, cork-cambiums in the paren- 

 chyma between the annual increments in the vascular 

 bundles and also within the pith. In the majority of cases 

 the endodermis was demonstrable by the presence of Cas- 

 parian dots, or else a cuticularised lamella was found in its 

 walls, either all the way round (as in the runners in Bart- 

 schia) or only on the inner and radial walls (runners of P. 

 capitata). 



The Leaf. All the species investigated have leaves 

 mesomorphic in structure. The cuticle is thin; in Veronica 

 fruticans a moderate thickening of the walls of the epidermal 

 cells takes place, the other species have thin walls. The 

 lateral walls of the epidermal cells of Castilleia pallida are 

 almost straight, of the other species more or less decidedly 

 undulating; in Euphrasia arctica and Bartschia alpina the 

 difference between the epidermis of the upper and lower 

 surfaces is in this respect inconsiderable; in the species of 

 Veronica and Pedicularis I found that the epidermal cells of 



