158 SCURFS. [HOOK i. 



4. Of Scurf. 



SCURF consists of thin flat membranous discs, with a ragged 

 margin, formed of cellular tissue, springing from the epi- 

 dermis. It may be considered as a modification of hairs; for 

 it differs from those bodies only in being more compound. 

 It is of two kinds, Scurf, properly so called, and Ramenta. 



Scurfs, properly so called, are the small, roundish, flattened, 

 particles which give a leprous appearance to the surface of 

 certain plants, as the Elseagnus and the Pine Apple. (Plate 

 I. fig. 10. b.) They consist of a thin transparent membrane, 

 attached by its middle, and, owing to the imperfect union, 

 towards its circumference, of the cellular tissue of which it is 

 composed, having a lacerated irregular margin. A scale of 

 this nature is, in Latin, called lepis, and a surface covered by 

 such scales lepidotus not squamosus, which is only applied 

 to a surface covered with the rudiments of leaves. Scurfs are 

 the poils en ecusson (pili scutati) of De Candolle. 



A very beautiful and peculiar form of scale has been re- 

 marked on the under surface of the leaf of " Adelia neriifolia," 

 by Dr. Willshire, who describes it thus : " It consists of two 

 circular layers of cellular membrane, the one layer of much 

 smaller diameter than the other, puckered and plaited, and of 

 a saucer-shaped form ; it is fixed by its centre, which appa- 

 rently is connected with a gland having coloured contents. 

 From this form of scale, through that met with on Elseagnus 

 conferta, I think transitional states may be seen to the stel- 

 late hairs of many of the Euphorbiacese and Malvaceae ; in 

 fact, upon the peculiar adhesions taking place between the 

 cells depends the appearance of the stellate hairs or the scale 

 of Adelia and Elseagnus." 



Ramenta (Vaginellae) are thin, brown, foliaceous scales, 

 appearing sometimes in great abundance upon young shoots. 

 They are particularly numerous, and highly developed, upon 

 the petioles and the backs of the leaves of Ferns. They 

 consist of cellular tissue alone, without any vascular cords, 

 and are known from leaves not only by their anatomical 

 structure, but also by their irregular position, and by the 



