LIFE HISTORY OF PINUS 15 



was desirable to store material for a few days or weeks, pure 

 cedar oil was found to be a much better medium than 75 ft 

 alcohol, which is commonly used for temporary storing of ma- 

 terial. For the purpose of getting specimens into pure paraffin 

 they were transferred to tiny wire-gauze baskets and carried 

 successively into 25, 50 and 75$6 paraffin in cedar oil, and 

 finally into pure paraffin with a melting point of "54, in which 

 they were at last imbedded. This is a very convenient and eco- 

 nomical method for getting material through the paraffin oven. 

 The grades of cedar oil in paraffin can be kept in the bath a 

 long time and used repeatedly with impunity, and material can 

 be carried in the little baskets from bottle to bottle much more 

 quickly and with less liability to injury than in any other way 

 with which I am familiar. At the time of fixing, a small piece 

 of paper, bearing the number, in pencil, corresponding to the 

 number of the entry in the record book, was placed in each 

 bottle, remained with the material through all the changes which 

 followed, and was finally imbedded in one corner of the paraffin 

 block containing the specimens. 



Staining. A Minot-Zimmermann revolving microtome was 

 used in cutting the material. The sections varied in thickness 

 from 4 to 13.6 microns, but by far the greater number were 

 made 6.3 microns thick. They were fastened to the slide by 

 means of albumen-fixative, and the slides were labelled with 

 glass-ink. In preparing this ink, a paste was made of the best 

 English vermilion in sodium silicate, and sufficient water was 

 added to give the proper consistency for writing. Glass-pen- 

 cils, Higgins' waterproof ink, both with and without collodion, 

 and other methods for marking slides were tried ; but I have 

 never found anything at all comparable, for excellence, with 

 the glass-ink. When properly prepared it is not dissolved dur- 

 ing the process of staining, but can be removed from slides or 

 dishes, when desirable to do so, by heating in a strong solution 

 of potash or in gold dust. 



As is usual in cytological studies, considerable experimenta- 

 tion was necessary before satisfactory stains were obtained. 

 Among the stains tested were Rosen's ('92) fuchsin and methy- 

 lene-blue method ; the Ehrlich-Biondi-Heidenhain mixture, as 



