120 THE AMERICAN MONTHLY [May 



rotund in form, the interior cells hy:ilinc ami with rich proto- 

 plasmic contents, the peripheral cells dark brown in color. 



In some cases these measnreil So to loo -i. ami tVequenlly tln» 

 depth of the welt of dark mycelium in which they were seated 

 exceeded this nieasurenient. 



Late upon the surface of this jjrowth free threads arose in a 

 pn)cumlH"nt, assur«jeut. or nearly erect position. All of this de- 

 velopment on the bean stems took place in ten tlays. Theblack- 

 eninj; of tiie stroma in the pustule on the stems of tiie jirivct is 

 proliablv analajjous to the dark weft of mycelium developed over 

 the bean stems in the culture. 



B»TAMtAL DbIT., CoKNBLI. 1"n|VBHMTV. 



A riH'iiiiiatic IJiihhlc H(Mn(>V('r. 



Hv A. P. WKAVICR, 



lACKSON MISS. 



Being annoyed with air bubbles in my mounts, 1 have made a 

 simple air-pump for removinjj; them, as follows: Take a small 

 rubber svrinj^e, the packiu"; on the cylinder of w^hich ought to be 

 adjustable so as to fit the bodv of the syrino;e rather tijijhtly ; cut of\ 

 the no/zle rather close to the body, and bore a hole 3 mf/i. in di- 

 ameter near the top of the latter, so that the packin<^ will always 

 be beU)w the hole. Cut from an old rul)ber l)oot two washers 

 2.5 CM. in diameter and with a central aperture of 2 rw. ; cement 

 these washers together with Red Cross cement (such as is used 

 for mendlngpuncturesin pneumatic bicycle tires) ; cut from theboot 

 two more washers of the same outside diameter and with a cen- 

 tral hole a little smaller than the nozzle of the syringe ; cement 

 these last two washers together also, and cement them to the first 

 two preparetl ; vou will now have a shallow chamber a little 

 larger than the cover-glass. Force the nozzle of the syringe 

 through the opening in the two top plates and firmly cement it 

 there. All these joints must be air-tight. 



To use the instrument, place the slide on a sniocjth surface, 

 wet the under surface of the rubber washers and apply the same 

 to the slide with the cover-glass in the shallow chamber. To 

 make a good air-tight contact with the slide, grasp the syringe 

 with the left hand and allow tlie lower side of the latter to hold the 

 washers firmly to the slide. Tiie hole drilled in the syringe is to 

 act as a trap or valve and is to be tightly covered with the first 

 finger of the left hand (keeping the latter in position, grasping 

 the svringe and holding the washers to the slide) at each downward 

 stroke of the piston and uncovered at each upward stroke. I'his 

 is, of course, done to prevent the entrance of air to the vacuum 

 chamber beneath, after it has once been exhausted. I have found 

 that three or four strokes are sufficient to bring all bubbles to the 

 surface of the mountincj Huid and cause them to burst. 



