84 



Methods in Plant Histology 



be allowed to dry 1 . Use square or oblong covers for such mounts, 

 reserving round covers for glycerin mounts. If material is abundant, 

 use as many sections as you can cover conveniently. If you have 

 used several stains with the same material, select for each mount 

 sections from the different stains. In ordinary wood sections each 

 mount should show the three most important views, transverse, 

 longitudinal radial, and longitudinal tangential sections. It is 

 wasteful to use three slides and three covers to show these three 

 views, or to make a mount containing only a single section of the 

 rhizome of Pteris. 



Put the label at the left. Write first the genus and species; then 

 indicate what part of the plant has been mounted. The date on 



\o. 



FIG. 17. The label. 



which the material was fixed is often valuable. After a year or so, 

 the date of making the mount may be of interest in indicating the 

 relative durability of stains. The beginner is likely to write also the 

 stains used, and other details, which he will find quite unnecessary 

 after a little experience. Fig. 17 illustrates a good style of labeling 

 and mounting. 



The following is a convenient summary of the foregoing processes, 

 beginning with the sections in 95 per cent alcohol : 



1. Sections in 95 per cent alcohol. 



2. Safranin, 12 to 24 hours. 



3. 50 per cent alcohol, with or without acid, until color is right, gener- 

 ally about 2 to 10 minutes. 



4. Water, 5 minutes, changing frequently. 



5. Delafield's haematoxylin, 3 to 30 minutes. 



6. Water, 5 to 10 minutes, changing frequently. 



7. Water slightly acidulated, 5 to 10 seconds. 



8. Water, to wash out acid, 20 to 30 minutes. 



