121 



the study of a powaur it may be ;.t;iiiu'(l dift'erentially to correspond with 

 the staining which can be employed upon various sections made of the 

 original crude material, it becomes much easier to refer the minute 

 granules and fragmentary elements to the tissues from which they orig- 

 inated. 



There are two ways by which we may produce differentially stained 

 powders for microscopical examination. The first and simplest is to mal^e 

 thiclv (i{;-i^mm) transverse sections of the tissues to be studied. These 

 may then be stained in the usual mannei*, after which they are triturated 

 in a mortal- to a No. 60, 80 or 100 powder, as the case requires. Such 

 powders are differentiallj' stained in a satisfactory manner, but the frag- 

 ments and cell masses often show truncated ends, due to sectioning, 

 which are not found in powders produced wholly by grinding. 



While the above process is an aid to the proper understanding of 

 powders it is not of direct service in the great number of cases in which 

 the microscopist is required to determine the identitj' and purity of 

 powders. In such instances any staining method to be of service must 

 enable the operator to differentially stain the powders directly. This may 

 be accomplislied by placing about i/4 or % gm. of the powder in a glass 

 tube (50 to 60mm long and 10 to 15mm in diameter), one end of which 

 has been closed by tying over it a piece of closely woven white silli cloth. 

 Resting on this cloth bottom the powder may be treated with the various 

 bleaching fluids, washed, double stained, deliydraded and cleared for 

 mounting by allowing the tube to stand in watch glasses into which the 

 stains and reagents have been poured. In this way a number of powders 

 each in a separate tube may be treated at the same time. Owing to the 

 great cajiillarity of fine powder it may often be necessary to promote the 

 drainage and washings by blowing on the free end of the tube with the 

 mouth; in this way it is possible to make rapid transfers from one reagent 

 to another. 



Crtptogamic Collections Made During the Year. 

 By M. B. Thomas. 



During the past year some very interesting collections of cryptogams 

 have been made in the local flora of Montgomery County. 

 9— A. OF Science. 



