1896.] MICROSCOPICAL JOURNAL. .379 



ial may be very satisfactorily and economically ob- 

 tained. 



The old method of preservino; in strong alcohol shriv- 

 elled the specimens to such an extent that the use of 

 strong swelling reagents (alkalies or acids) was necessary 

 to show anything like the proper degree of detail of 

 structure, and while these methods were good for the 

 ordinary tougher species, and when applied by students 

 of some experience, yet they were very unsatisfactory 

 when applied to the more delicate forms or when used by 

 the more inexperienced manipulators. 



The use of the weaker alcohol, 50-70 per cent accord 

 ing to the particular specimen to be preserved, was better 

 yet proved decidedly unsatisfactory for the more delicate 

 forms. 



The ordinary English method of fixing in a saturated 

 solution of picric acid and preserving in strong alcohol 

 is a very good one, especially for specimens to be im- 

 bedded in paraffin or for special work in connection with 

 particular problems. Better still is fixing in some special 

 solution such as a saturated solution of picric acid, 0.5-1 

 per cent chromic acid. Perenyi's fluid, Hermann's mix- 

 ture, etc., and transferring through the ordinary grades 

 of alcohol, or by dialysis, up to 70 percent strength and 

 preserving in that. 



Such material is in excellent condition for imbedding 

 in paraffin orcelloidin. but for the ordinary class work, 

 for manipulation by the student himself, the specimens 

 must generally be transferred again to water. 



But the preparation by these methods of material for 

 a large class in often a considerable task. The more 

 delicate forms too are seldom in a thoroughly satisfactory 

 condition. 



It has been found to faciliate the class-Avork on all the 

 cryptogams very much to use freezing methods in the 

 preparation of sections for the class, and either to have 



