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 Absynthium, and the frequently-mentioned Edel- 

 raut, Artemisia Mutellina, 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 



Fig. 78. Covering Hairs. 



1 Floccose hairs of Verbascum thapsiforme. 2 Tufted hairs of Potentilla cinerea. * T-shaped hairs of Artemisia mutellina. 

 * Actinia-like hairs of Correct speciosa. * Scutiform scales of Elceagnus angustifolia. 6 Stellate hairs of Aubretia 

 deltoidea. x about 50. 



the leaf -surf ace), 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. 78 6 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 8 , has a particularly beautiful appearance in 



