Scrophulariaceae. 505 



the lower surface had the most decidedly undulating lateral 

 walls. 



The lateral walls of the epidermis in Veronica alpina, 

 Castilleia pallida and Euphrasia arctica are without sculp- 

 ture; in the other species they are poröse; in Veronica fru- 

 ticans and Pedicularis euphrasioides, flammea and Oederi the 

 pores are distinct and alternate with flanged thickenings, 

 whereas they are fine in Bartschia alpina and the other 

 Pedicularis spp. It should be noted, however, that the epi- 

 dermal cells of the lower surface which bear the large glan- 

 dular hairs have (except in P. lanata) very vigorously devel- 

 oped flanged thickenings in the Pedicularis spp., and usually 

 also in Euphrasia and Bartschia-^ also their walls are, on the 

 whole, distinctly thicker than those of the surrounding epi- 

 dermal cells. 



Stomata occur exclusively on the lower surface of the 

 leaf in the Pedicularis spp., nearly equally on both surfaces 

 in Veronica fruticans, V. alpina, Castilleia pallida and Eu- 

 phrasia arctica, and more abundantly on the lower surface 

 in Veronica officinalis and Bartschia alpina. The guard-cells 

 are on a level with, or raised only slightly above the leaf- 

 surface; they are surrounded by 3 — ^8 cells. 



The mesophyll in all cases is rather lacunose and consists 

 of thin-walled cells. In Castilleia pallida it may be almost 

 homogeneous ; 2 — -3 layers of short palisade-cells occur in the 

 Veronica spp., Euphrasia arctica and Bartschia alpina. Of the 

 Pedicularis spp., P. euphrasioides, capitata, hirsuta, flammea, 

 Oederi, and frequently lapponica, had 1 — 2 layers of typically 

 developed palisade-cells; they were shorter and broader in 

 P. Sceptrum carolinum, sudetica and lanata. 



In P. flammea and Oederi there were large air-chambers 

 between the spongy parenchyma and the epidermis of the 

 lower surface (cf. Fig. 46, A). In all the species investigated, 



