* 



Curtis : Turgidity in Mycelia 3 



cover glass with a film of dilute gelatine and covered with a nar- 

 row strip of silk paper or any thin unsized paper about 5 mm. 

 long and 1 mm. wide. Each end of this paper had been previ- 

 ously touched with melted shellac so that a drop adhered to it. 

 By applying a hot rod over the drop of shellac it is melted, 

 fastening the paper firmly to the cover glass. In this way 

 the paper is spread out smoothly over the spores, holding 

 them firmly on the glass. The spores will germinate and push 

 out from under the strip of paper and the mount can be 

 handled without fear of destroying the hyphae, readily changed 

 from one fluid to another and the growth studied in a hanging 

 drop with ease. Furthermore the same hyphae can be observed 

 during the entire experiment, and any error that might arise 

 from a change from one filament to another can be avoided. 

 Every precaution was taken to secure uniform external conditions. 

 Repeated tests during the day showed that the ordinary variations 

 of temperature produced no effect on the turgor force and rarely 



i 



was there a variation of over one and a-half degrees during the 

 majority of the experiments. The work prosecuted in the sum- 

 mer, however, was subject to a much more considerable range of 

 variation than in the winter. 



In regard to illumination, the alternation of light and darkness 

 and different degrees of light intensity gave no different results 

 from those obtained when the plants were grown in the dark room 

 and received illumination only from the mirror of the microscope 

 for a few moments at the time of the observations. For the pur- 

 pose of uniformity all the cultures and examinations were made 

 under the same conditions so far as possible and the greater part of 

 the experiments were conducted under exceptionally uniform con- 

 ditions. 



The spores used were always taken from recent cultures since 

 they produced plants of more uniform vigor. But even with this 

 precaution here was presented the most serious difficulty in the 

 work. For, having sown a few spores on a cover glass, not only 

 do some fail to germinate but some are very slow to grow and 

 others show a great vigor. Again, some will produce almost from 

 the start a branched series of filaments and others will develop lat- 

 eral branchlets only after extended growth. Now it is evident that 



