THE HAIRS OF PLANTS. 



65 



Hairs are minute, semi-transparent, transparent, or opaque thread-like processes, 

 attached to the cuticle by one 

 extremity, and remaining free 

 at the other (Fig. 112). They 

 are always of a cellular charac- 

 ter, the cells, if more than one, 

 being larger and more numer- 

 ous at the bottom, and then 

 piled one upon the other, and 

 laid in one or more rows, until 

 the apex is attained, with its 

 single elongated, rounded, or 

 pointed cell. The figure and 

 minute anatomical characters 

 vary considerably, so that the 

 above general description may 

 require modification when ap- 



a 



a hair. 



mity. 



hair. 



d 



a, a gland, surmounted by 

 b, a hair with an enlarged and secreting free extre- 

 >, e, simple hairs with pointed extremities, d, branched 



plied to individual instances. 



Thus the hairs of certain plants 



are attached by their middle, 



and have both ends free. Such 



are those of Indigofera, Cap- 



sella, and Astragalus asper ; but 



in order to bring these within the definition above-mentioned, it is customary to assert 



that it is not one single hair attached by its middle, but two hairs springing from the 



opposite sides of an elevated cell. Such, doubtless, is the correct 



explanation of hairs which assume a stellate or star-like form, and 



which are really clusters of hairs attached each by one extremity. 



This variety is met with readily on the leaves of the MaUows, in 



which, with the assistance of a small hand magnifier, the stars may 



be perceived. The most beautiful illustration, however, is that of 



the hairs of the Deutzia scabra and corymbosa (Fig. 102), and the 



Elceagnus, which, as has already been demonstrated, are coated with 



a layer of silica or flint. They are very resplendent when viewed 



with the light thrown upon, and not through them that is, as 



opaque objects, and may aptly be compared to the jewelled star of 



the Most Noble Order of the Garter. 



Certain hairs are bent at the points of articulation of the cells, 

 whilst others have their points only thus distorted. This latter 

 variety is seen familiarly in the common teasel (Dipsacus), and has 

 been used with much sagacity by cloth-workers, for the purpose of Fig. 113.-A prickle 

 raising the nap of the cloth. The extremity is hooked, and by that f^/ Sd^S" 

 means adheres to an object with great pertinacity, as any one may * fuUomtm)', 

 prove by placing the fruit of the teasel in his hair (Fig. 113). f sistin s ? m eih a a t 



Another and very interesting modification is that in which the bent 



hair consists of a single ceU, but having an elastic spiral fibre coiled 



up within it 



cell, thick- 

 by layers, 

 embraced at 



Such hairs are almost imperceptible, so long as they the base by amass 

 sometimea with a crackling 



