322 



PROTECTIVE AllHANGEMENTS OX THE EPIDERMIS. 



species of woi-ni woods; the >Soiitli European Artemisia arborescens and arrjentea, 

 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 <if" 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 





■L^' 

 m 



Fig. 78.— Covering Hairs. 



' Floccose liairs of Verbascum thapsiforme. 2 Tutted hairs of PotentUla cinerea, s T-shaped hairs of Artemisia mutellina. 

 < Actinia-lil^e hairs of Correa speciosa. ' Scutiform scales of Etceagnut angustifolia. « Stellate hairs of Aubretia 



dettoidea. x about 50. 



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

 above the epidermis, is prolonged iu 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" and TT"). 

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

 tigs. 77*). In rare cases they have a comj^aratively large central portion, and are 

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

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

 represented in figs. 77 ^ and 77 *, has a particularly beautiful appearance in 



