HAIRS. 



91 



the stems and leaves of the Wall-flower, or Gilly-flower (Cheir- 



anthus Cheiri), we see spindle-shaped structures (Fig. 33, A), 



with narrow cavities obliterated towards the two ends. These 



unicellular spindles are covered on their outer surface with pro- 



tuberances, less numerous larger ones and more numerous 



smaller ones between them. As the spindles are all directed 



parallel to the long axis of 



the leaf, we can see in what 



direction cross - sections of 



these should be taken, 



though thin sections are 



not easy to obtain. As it 



is desirable to hit upon the 



hair at its point of insertion 



in the centre of its length, 



numerous sections should 



be taken in order to increase 



the chance of success. 1 We 



see (Fig. 33, 5) that the place 



of insertion of the hair lies 



somewhat sunk, and that 



the epidermal cell which 



broadens out into the body 



of the hair is narrower than 



its neighbours, that at the 



base it is somewhat swol- 



len, rounded, and extends 



fiirtViov infrk 



larthei into 



ing tissue. It forms the 



, i , . 

 " toot ot the hair. Lon- 



gitudinal sections through the leaf show that the foot is not 

 broader in the long direction of the hair than in the cross direc- 

 tion. We can readily satisfy ourselves that the cavity of the 

 foot passes without interruption into the cavity of the body of 

 the hair. We can obtain a still more complete idea of the form 

 of the foot if we lay a thin surface-section with the under side 

 upwards. The foot is circular in section. It can now be seen, 



1 As similar hairs are found longitudinally placed upon the young stems, 

 and these latter are much easier to prepare cross-sections of, they may offer 

 alternative material, and if preserved in alcohol are so much the better. 



[ED.] 



F IG . 33, j and B. From the under side of 

 oiivvnrinrl the leaf of Cheiranthus Cheiri. A , the hair seen 



surround- from above (x 90) ; ,6, in cross-section (x 240) ; 



C', from the under side of the leaf of Matthiola 

 annua ; hair seen from above (x 90). 



