286 



Transactions. 



and internal ones are much more so. There is a thick, rough cuticle. 

 Some of the epidermal cells are produced into hairs like those on the 

 leaf. 



The cortex is a wider band than in the peduncle. The cells of the 

 outermost layer have their walls slightly thickened, but the rest of the 

 cortical cells have thin walls. There are only very small intercellular air- 

 spaces. The cells contain a very few small chloroplasts in a peripheral 

 layer of protoplasm. The cortex forms a water-storage tissue. 



The endodermis and the phloem are the same as in the peduncle, 

 except that the phloem is a wider zone of tissue. The cambium is easily 

 seen. 



Fig. 12. — Wahlenbergia albomarginata. Transverse section of stem (x 48). 

 a, unicellular hair ; b, endodermis ; c, phloem ; d, cambium ; e, xylem. 



The xylem consists of vessels of small diameter ; there is a large 

 amount of xylem parenchyma. The pith is formed of large thin- walled 

 cells which are closely packed together and are not lignified. 



30. Celmisia longifolia Cass. var. gracilenta T. Kirk. 



Hahit.— This plant is a small, tufted, perennial herb. The leaves' are 

 all radical, simple, and erect ; they are 3-7 in. long, iV~F ^^- broad, and 

 the margins are re volute. The whole leaf is covered with silvery -white 

 tomentum, and is produced into a broad sheathing base, which is also 

 covered with tomentum. The sheathing leaf-bases are persistent, and are 

 used to store water {cf. with " tunic " grasses — e.g., Poa Colensoi). 



