Scrophulariaceae. 453 



structure, according to the investigations of L. Kocii^ and 

 E. Strasburger, is found in the aereal stems of Sedum 

 populifolium L. 



The Leaf. The epidermis of the upper surface has 

 lateral walls, varying from straight to slightly undulating; 

 only along the edges of the sections are the undulations more 

 marked, very much as on the lower surface (Fig. 33, D and 

 E). The lateral walls are thin, and faintly and distantly 

 porose; only those cells on the lower surface which bear 

 glandular hairs, have, as is also the case in the other species, 

 thicker and more highly porose walls. The transverse section 

 shown in Fig. 33, A, exhibits the lacunose structure of the 

 mesophyll: the 1 — 2 layers of short pahsade-cells, which tend 

 to be almost isodiametric, and the usually abundantly- 

 branched cells of the spongy parenchyma; a surface-view of 

 the latter cells is shown in Fig. 33, C. Stomata occur only 

 on the lower surface; the guard-cells are on a level with, 

 or project only slightly above, the epidermal cells, which 

 surround them to the number of 4 — 6. Chlorophyll occurs 

 abundantly in the whole of the mesophyll, and also in the 

 epidermis of the lower surface. Non-glandular hairs are totally 

 absent; glandular hairs of the usual type occur in great 

 numbers under the secondary veins, and the veins of higher 

 order of the leaf-sections. 



Pedicularis capitata Adams. 



Herbarium-material from St. LawTcnce Bay, King 

 Wilham's Land (Gjoa Harbour), Ellesmere Land, Kotzebue 

 Bay, Island of Iglorlik and from near the Taimyr River. 



1 L. Koch: Untersuchungen liber die Entwåcklung der Crassula- 

 ceen. Heidelberg, 1879, and E. Strasburger: Ueber den Bau und die 

 Verrichtungen der Leitungsbanen in den Pflanzen. Jena, 1891. pp. 324 

 —326. 



