FREEHAND SECTIONS 99 



after this stain is satisfactory and all acid has been washed out, stain 

 for 1 or 2 minutes in aqueous eosin, erythrosin, or acid fuchsin; place 

 directly into 95 per cent alcohol for a few seconds (merely to save the 

 absolute alcohol), then into absolute alcohol for about 30 seconds, and 

 then into clove oil. Mount in balsam. The epidermis is likely to curl 

 and, unfortunately, patience seems to be the only remedy. In mount- 

 ing, be careful to get pieces from both sides of the leaf, and be sure 

 that the pieces are outside up. The inside of the epidermis is usually 

 more or less rough, on account of the mesophyll torn off with it. Sedum 

 piirpurascens will show various stages in the development of stomata, 

 even in epidermis stripped from mature leaves. The epidermis of the 

 Sedums strips off very easily. If the large Sedum maximum is avail- 

 able, it is not difficult to strip off pieces 2 or 3 centimeters wide and 

 several centimeters long. There is not much tendency to curl. The 

 pieces may be spread out flat in a Petri dish, fixed in the chromo- 

 acetic-osmic solution, just recommended for fern prothallia, or in this 

 solution without the osmic acid. Wash in water, stain in Delafield's 

 haematoxylin and eosin, or in safranin and gentian violet. Then wash 

 in water and run up through a series of alcohols — 5, 10, 20, 35, 50, 70, 

 85, 95, and 100 per cent — about 30 minutes in each grade, except 85, 

 which should be allowed to act for a couple of hours or overnight. 

 Then transfer to clove oil, xylol, and balsam. This is a more tedious 

 method, but it is worth the trouble. We have had the best results with 

 the haematoxylin and eosin combination. 



Other objects. — The cases just given will suggest other objects 

 which might be mounted by such methods. Nearly all objects which 

 used to be mounted in balsam without sectioning are now handled 

 successfully by the \>netian turpentine method. 



