— 14 — 



In regard to the second point, there may cases occur 

 where no cuticle exists on the hair, but among those 

 here described the first 50 were treated with concentrated 

 sulphuric acid and in no single instance can I say with 

 certainty that the cuticle was entirely absent from the 

 hair. This was the more thoroughly tested, as the ab- 

 sence of the cuticle would have added to the probability 

 of the hypothesis assumed. In many cases there was a 

 difference in the color produced by the action of the acid, 

 the first cell often coloring darker than the long end cell. 

 This difference was more marked in the hairs of the second 

 class of leaves, where the stem often assumed a much 

 darker color than the rest of the hair. Here also the 

 action of the acid often left very little, if any, traces of 

 cuticle from the horns or branches, but that part in im- 

 mediate connection with the epidermis seemed to be 

 affected exactly as the epidermal wall itself was, that 

 is, there were always traces of a thin cuticle left on the 

 glass. That this was sufficient to retard the passage of 

 water through the membrane but very slightly, was pro- 

 ved satisfactorily by experiment. 



One of the best examples of the first class is Heli- 

 chrysum petiolatum D.C. The leaf is small, filzig on both 

 sides, but much stronger below, and on plunging it in water 

 it is at once wetted, shows no silvery sheen. A cross section 

 through the leaf shows a filz on the under side about 

 three times as thick as the leaf itself; above on the older 

 leaves it is much less in thickness and some times wan- 

 ting. The hairs stand erect (perpendicular) from the sur- 

 face as far as the living cells extend; these are from 

 two to four in number, about 25 mik. in diameter and 

 75 mik. in length. The end cell, which joins the last 



