182 The Microscope. 



straight and distinct, Avhile in the older leaves a film spreads- 

 widening and extending over the surface somewhat irregularly 

 yet Avithout disarranging the little heaps themselves, or without 

 taking any part of their substance. If you should go no further 

 than this in the examination you will have seen a beautiful thing 

 in the common Hemlock leaf, and one that can be examined at 

 any time without the least trouble. But having progressed thus- 

 far, the subject will become interesting and the microscopist will 

 determine to know what these things are, and if possible where 

 they came from. 



With a sharp razor cut away the projecting midrib, and then 

 make some free hand sections of the leaf, cutting the silvery 

 layer from] the surface to which it is attached. Mount the sec- 

 tions in glycerine, and examine them by transmitted light. 

 What has become of those white balls? They are now repre- 

 sented by little dots of opacity so dark they are almost black. 

 Rack up the condenser, if necessary, and get a strong light on 

 them. Still in the regular order and that evenly distributed se- 

 quence. A sudden thought will perhaps strike you as you are 

 looking and wondering what these common leaves have got to 

 tell. What secret has here been waiting all these years since you 

 have had a microscope and since you have almost every day 

 been passing this Hemlock hedge? You have of course noticed 

 the green and tender leaves appearing in the spring ; you have 

 observed that they change color and lose their delicate tint as 

 the season advances, and you have taken the leaves into your 

 hand and have seen the silvery lines on the lower surface, but 

 that is all. You have perhaps nevar thought that these lines of 

 whiteness might be anything but a colorless portion of the cuti- 

 cle. Now this must be investigated. 



While you are looking an idea leaps through your mind, and 

 you set about proving it. But how? The dots are too small to 

 be picked off with a needle point. When scraped away with the 

 knife the result is microscopical chaos. What can be the char- 

 acter of the substance? It is not resinous in the ordinary bo- 

 tanical sense of that term, for it is not sticky to the touch. It 

 must be something analogous to the bloom on the plum, on the 

 cabbage leaf and others. Then it should be wax. If wax it is 

 susceptible to heat. No sooner thought of than executed. Over 

 the lighted lamp goes that section for the fraction of a minute. 



