322 



PROTECTIVE ARRANGEMENTS ON THE EPIDERMIS. 



species of wormwoods; the South European Artemisia arborescens and argentea, 

 the Artemisia sericea and laciniata belonging to the steppes and Siberian flora, the 

 Common Wormwood, Artemisia Absynthiwm,, and the frequently-mentioned Edel- 

 raut, Artemisia Mutellinu, growing on the rocky crags of mountain heights — all 

 owe their silky appearance to these T-shaped hair-structures. 



It may also happen that the cell which is elongated transversely (i.e. parallel to 







ffrffi 



Fig. 78. — Covering Hairs. 



- 



1 Floccose hail's of Verbascum thapstforme. • Tufted hairs of Polentilla cinerea. 8 T-shaped hairs of Artemisia mutellina. 

 * Actinia-like hairs of Correa speciosa. fi Scutiforui scales of Elwaynus angusttfolia. ° Stellate hairs of Aubietia 

 dtltoidea. x about 50. 



the leaf-surface), and which is the uppermost of the small group of cells projecting 

 above the epidermis, is prolonged in three, four, or even more directions, so as to 

 have a stellate appearance. Thus the covering of the leaf is seen to consist of three, 

 four, or many-rayed stars, each supported on a short stalk (see figs. 7S 15 and 77 6 ). 

 The rays of the stellate cells are frequently forked, as in Draba Thomasii (see 

 figs. 77 9 ). In rare cases they have a comparatively large central portion, and are 

 only divided at their circumference into short rays; they then look exactly like 

 small sunshades spread out over the leaf-surface. This elegant form, which is 

 represented in figs. 77 7 and 77 s , has a particularly beautiful appearance in 



