Journal of Applied Microscopy. 



543 



METHODS IN PLANT HISTOLOGY. 



Charles J. Chamberlain. 



VIII. 



ALGAE. 

 Diatoms. — Diatoms and Desmids have been variously classified, and their 

 position is not yet fully determined. A method for mounting fossil forms has 



already been given. Living forms 

 are often found clinging in great 

 numbers to filamentous algae, or form- 

 ing gelatinous masses on various sub- 

 merged plants. To obtain mounts of 

 the frustules, use the method given 

 in the March number of the Journal. 

 It is more difficult to get really good 

 preparations showing the nucleus and 

 chromatophores. If the diatoms are 

 clinging to filamentous algse, the algae 

 with the diatoms attached may be put 

 into chromo-acetic acid (twenty-four 

 hours), washed in water, stained, 

 passed up through the alcohols, and 

 cleared in xylol, or, better, in clove 

 oil or bergamot oil, which do not dry 

 up so rapidly. Here the diatoms may 





D 



B 



Fig. 1 8. Diatoms. 

 A. Pleurosigma angulatum. 

 tylis. C. Synedra biceps. 



X255. 

 B. Navicula dac- 

 D. Gomphonema 



sphasrophorum. E. Triceratium sp. 



be picked or scraped off from the other algae, 

 which will probably have become much 

 shrunken by this treatment. Mount in bal- 

 sam. Haidenhain's iron alum hsematoxylin is 

 recommended for the nucleus and the centro- 

 some, which is quite prominent in diatoms. 

 Delafield's haematoxylin and erythrosin give a 

 good view of the nucleus and chromatophore. 

 If a glycerine mount is preferred, the iron 

 alum haematoxylin is a good stain. 



When the material is in gelatinous masses, 

 it may be fixed in chromo-acetic acid and im- 

 bedded in paraffin. There will, of course, be 

 some difficulty in cutting, and many frustules 

 will be broken, but there will, nevertheless, be 

 occasional views which show details better 

 than when the diatoms are mounted whole. 



Desmids. — When these forms are very 

 abundant they may be treated like the fila- 



Fig. 19. Desmids. X 255. 



From glycerine preparations. Not 

 stained. A. Cosmarium pectin- 

 oides. B. Closterium cucumis. 

 C. Staurastrum cornutum. D. 

 Arthrodesmus octocornis. 



