246 The Microscope. 



have not discovered it. Yet by a very simple method these ob- 

 jects as well as leaves may be made entirely or almost trans- 

 parent, so that the vessels and the cells may be studied at one'& 

 leisure and in comfort. By this treatment the hair-like and 

 glandular appendages and stomata are preserved in place 

 and in structure, the protoplasmic contents alone being con- 

 tracted toward the centre of the cells. It is a method that I 

 have stumbled on by accident, but one that I can recommend 

 to the microscopical botanist that desires to examine these parts 

 without destroying or disarranging any of the constituents. 



Place the petal, the anther, the whole blossom, or a part of a 

 leaf on the slide in a large drop of glycerine. See that it is 

 completely submerged beneath the liquid, and add a large cover 

 glass. It is best to use a slip without a cell. Then boil the 

 glycerine over the lamp flame until the parts are entirely trans- 

 parent or at least translucent, a condition that will arrive in a 

 short time. Do not allow the boiling to be so violent as to dis- 

 arrange the thin glass ; let it be so gentle that the bubbles will 

 run one by one to the edge of the cover and there break. If 

 the glycerine should become discolored, as will often happen 

 when leaves are under treatment, draw off the liquid by a wet 

 cloth and add fresh glycerine, repeating the process and the boil- 

 ing until the leaf is saturated. The use of glycerine and the 

 saturation of the cells form the secret of the process. The sat- 

 uration is easily accomplished with petals and similar delicate 

 parts ; with thick and opaque leaves the time demanded is longer,, 

 and the specimen may become only translucent. I have made 

 the thick and opaque leaf of the garden geranium, Pelargonium, 

 so translucent that there was no difficulty in examining the 

 hairs on the surface, the epidermal cells, the parenchyma and 

 vessels, with the cells of the epidermis on the opposite surface. 

 Of course there is a, limit to the thickness and to the opacity 

 that can be overcome, yet the method will be found exceedingly 

 useful. Leaves and petals do not entirel}' lose their color^ 

 although they become beautifully transparent. Of course the 

 specimens must be permanentl}' preserved in glycerine. 



The secret that the dealers have seemed to keep so carefully, 

 and that the books have ignored because apparently their au- 

 thors had not learned the process, is here placed at the reader's 

 disposal. I am sure that he will be pleased with the result of 



