1885.] 



MICROSCOPICAL JOURNAL. 



37 



ing the dessicated specimens of algge, 

 such as are preserved on paper in the 

 herbarium, with a sokition of caustic 

 potash, the cells resume their origi- 

 nal size and shape, so that they may 

 be studied microscopically. Any 

 medium that will restore the forms 

 of the cells adds greatly to the in- 

 terest and value of such a collection, 

 for the wrinkled, misshapen filaments 

 one sees when water alone is used 

 are far from attractive to the eye. 

 Mr. G. Lagerheim has prepared a 

 fluid for this purpose, which pos- 

 sesses some features worthy of note. 

 It is composed of water 5 parts, in 

 which is dissolved i part of fused 

 potassic hydrate, and 5.5 parts of 

 strong glycerin added. To examine 

 dry desmids, oedogoniums or other 

 algse the specimen is moistened with 

 water, transferred to a slide and a 

 drop or two of the solution added. 

 After spreading the algse in the fluid 

 it is heated gently over a flame. The 

 algae then swell and resume their 

 natural form. 



To mount the specimens, particular 

 species may be easily selected under 

 a low-power objective and removed 

 to a solution of potassic acetate or 

 glvcerin. Should it be desired to 

 mount the entire specimen under ex- 

 amination a little acetic acid may be 

 added to the mixture, which will 

 produce potassic acetate by combin- 

 ing with the potash, and the prepara- 

 tion sealed. 



Quantitative Estimation of 

 Micro-organisms in the Air. — A 

 convenient method of determining the 

 relative number of organisms in the 

 air in different places and at different 

 seasons is very desirable. Various 

 methods have been described from 

 time to time, in most of which a cur- 

 rent of air is directed against a sur- 

 face coated with glycerin, in which 

 the germs or spores are caught and 

 submitted to microscopical examina- 

 tion. 



These methods have served very 

 well, but it has alway seemed to us a 



very unsatisfactory means when the 

 character of the spores was an im- 

 portant question, for the reason that 

 it is not usually possible to dis- 

 tinguish spores generically or specifi- 

 cally by their appearance. Other 

 methods have been in use in v\^hich 

 the spores are collected in nutritive 

 media in which they are cultivated. 

 The latest form of apparatus for col- 

 lecting spores for cultivation is that 

 of W. Hesse. This consists of a 

 long glass tube — about 7*^ ^^^^- "^ 

 length and 3.5 cm. wide, covered on 

 the inside with sterilized gelatin. 

 Through this tube a current of air is 

 drawn at a regulated speed, and the 

 volume that flows through is meas- 

 ured. The spores are deposited on 

 the gelatin, and after a suflicient time 

 they germinate and form colonies on 

 the gelatin which become visible to 

 the naked eye. 



The relative number of spores in 

 the air at any time can be estimated 

 by counting the number of centres of 

 growth. Each kind of growth can 

 be isolated and cultivated by itself. 



Having obtained the colonies in 

 the tube, the organisms may be killed 

 by passing sulphurous acid gas 

 through it, and the appearance of the 

 growing colonies thus preserved as 

 a record for future comparisons. 



NOTES. 



— The first number of the Journal of 

 Mycology has reached us, and we are 

 pleased to welcome it among our ex- 

 changes. It is devoted to mycological 

 botany, special attention being given to 

 descriptions of North American species of 

 fungi. It is edited by W. A. Kellermann, 

 Ph. D., assisted by J. B. Ellis and B. M. 

 Everhart, and published at Manhattan, 

 Kansas. It promises to be a valuable 

 scientific publication, and we trust it will 

 receive ample support. 



— One of the most successful operators 

 in photo-micrography is Mr. Walmsley, 

 who is continually adding to his store of 

 fine negatives of microscopic objects. We 

 would not like to say he photographs all 

 the good specimens that pass through the 

 postal-club circuits, but he certainly pre- 



