^l<)0 Journal of Applied Microscopy 



used for cutting was the ordinary razor. By a natural assumption, — the razor 

 being the instrument with the sharpest edge then in use,— it was supposed 

 that a knife in the form of a razor would be the best for use with the micro- 

 tome. How utterly erroneous this notion is I shall have occasion to explain 

 later. In order to work with objects of different sizes and to be able to have 

 several embedded at once, Ranvier added to his microtome two or three tubes 

 which could be placed within it, one inside of the other, but this addition of 

 extra devices was not of much practical value. It will be observed that the 

 essential principles of Ranvier's microtome are the same as those of His. The 

 knife is moved by the hand, but is guided by being rested against the plate. 

 The object to be cut is raised by the screw. But whereas in His's microtome 

 the knife edge came down against the plate, in Ranvier's it passed freely across 

 the object, and in this way escaped the danger of injury which was inherent in 

 His's construction. Charles Sedgewick Minot. 



Harvard Medical School. 



On the Manipulation of Sections of Leaf Cuticle.* 



The cuticularization of the outer epidermal cell-wall is one of the most strik- 

 ingly variable structural features presented by the higher plants as a means of 

 adaptation of a species to the various climatic conditions which control trans- 

 piration. Not only do many species show evidence of having thus become 

 adapted to extreme humidity or aridity, for example, through generations of ex- 

 posure, but, as has been shown by the investigations of Kohl, Lothelier, and 

 others, individuals of the same species manifest a great capacity to vary in this 

 respect. I have recently made a very extended histological investigation of the 

 foliar cuticle of several species, and have gained some experience in the manipu- 

 lation of sections, which may be of some interest, although I have nothing essen. 

 tially new to offer. Having somewhat simplified the methods in common use, I 

 offer an account of my experience for what it may be worth. 



In the study of a thin cuticle, as a rule, very thin sections are required, two 

 micromillimeters, or even thinner, being usually found necessary. It would, no 

 doubt, greatly facilitate matters in collecting material simply to remove at once 

 a small strip of epidermis freed from the underlying veins. It is no easy matter 

 to keep a blade sharp enough to cut sections of such thinness, and the lignified 

 portions of the leaf have a distinct tendency to dull the edge. I found, for in- 

 stance, that it is much easier to keep the knife sharp when cutting through a 

 leaf grown in a saturated atmosphere than one of the same species grown under 

 normal conditions. To facilitate handling the object in the process of embed- 

 ding and trimming, it would, no doubt, be desirable to stain iti toto with some 

 easily removable stain before embedding. 



In my own experience, I have taken a very narrow strip of the leaf and em- 

 bedded in paraffine according to the usual process. The paraffine is trimmed 

 away under the lens until the surface to be cut is reduced to a minimum. The 

 blade of the microtome knife is adjusted in the slanting position, and the sec- 



* Read before Section G, A. A. A. S., Washington meeting, Dec. 30, 1902. 



