BOTANICAL GAZETTE. 261 



as follows: A stem with leaves attached is cut very obliquely (under water), 

 then attached to a glass slide, the cut surface being covered by a thin glass 

 cover or another slide. Some freshly-precipitated calcium oxalate is introduced 

 into the water under the cover-glass when the current passing into the stem is 

 made evident by the granules which are drawn to the mouths of the vessels, ac- 

 cumulating as little plugs at their openings and finally being sucked in. In 

 some experiments to verify these observations, made by Mr. J. M. Waugh un- 

 der my direction in the botanical laboratory of Purdue University, an improve- 

 ment upon the method used by Vesque was made. The method as before given 

 was successful, but only after repeated trials and with considerable difficulty in 

 properly illuminating the upper cut surface so as to make the grains of the 

 calcium salt visible. Thinking that other teachers may like to know just the 

 way to make this easy demonstration a success I give the details of the experi- 

 ment. 



The stem of the common Clematis of cultivation was selected because of its 

 relatively large vessels. This, after being cut obliquely with a razor, was at- 

 tached to an ordinary slide by means of two rubber bands and covered with 

 thin glass. The whole of this operation must be performed under water. The 

 superfluous water was then wiped from the slide and it was transferred to the 

 stage of the microscope. The stem must be illuminated from above, either by 

 the mirror, if that swings above the stage, the Lieberkuhn, or the side condens- 

 ing lens. The lenses best adapted for this observation are the f or f objective 

 with the 2-in. eye-piece. Instead of the calcium oxalate, indigo rubbed into a 

 thin paste with water was employed. The advantage of indigo over the white 

 calcium oxalate lies in the fact that it is very dark, and hence the small grains 

 can be easily seen. The process, as shown by these granules, is a very interest- 

 ing one. Some collect at the edges of the larger vesspls, and some pass directly 

 into the cavity. The observations carried on by Mr. Waugh seem to show that 

 the cross between the imbibition and cavity theories is nearer the truth than 

 either. The granules stick against the edges of the cut wall because water is 

 imbibed by it, and the others continue up the cavity of the vessel because of 

 the current there. Suddenly pinching the stem sets the current backwards, and 

 quickly removing the leaves stops it altogether. — C. R. B. 



EDITORIAL NOTES. 



The subject of bacteria is beginning to receive the attention, at the hands 

 of the medical fraternity, that its great importance merits. Two notable works 

 have jnst appeared from the press of W. T. Keener, Chicago, on bacteria and 

 their relation to disease, by Drs. Gradle and Belfield, of the Chicago Medical 

 Colleges. Both works are carefully written, and will prove interesting reading 

 to others than the class to whom they are specially addressed. 



Fungous plants, as a source of food, are receiving increased attention in 

 both this country and Europe. A monthly journal, specially devoted to them, 



