1500 



Journal of Applied Microscopy 



In case the plate of the klinostat is too small for the attachment of the basin, 

 it must be fastened to a circular wooden plate, which is screwed to the plate of 

 the klinostat and also serves for securing the cover clamp. The cut shows the 



manner of securing the cover and the dish. 

 The clamp A is made of strong, elastic wood 

 with disks of rubber under the extremities 

 of the arms ; one end of it slips into a loop 

 of wire, a strip of brass at the other end 

 hooks to the wooden plate P. The dish is 

 held from slipping sideways by four pegs in 

 the wooden plate, which may be covered 

 with short pieces of rubber tubing. The 

 seedlings for use should be attached to short 

 wooden bars, which are fastened to the pegs 

 inside of the dark chamber by means of 

 two rubber bands. The strength of the centrifugal force, in terms of the attrac- 

 tion of gravity, may be calculated for the pegs from the following formula : 

 4 TT R (in meters) 4 tt^ 



gt2 



4.024 



X 



R 



^ 4.024, a constant. 



= no. of g (gravity). 



R = radius expressed in meters. 



t =: time in seconds of one revolution of the chamber. 



If the centrifugal force is small, i. e., less than three times the force of 

 gravity, the seedlings may be attached to the wooden bars in the ordinary method 

 by the use of rubber bands and strips of blotting paper ; but if the centrifugal 

 force is considerable, I have found it better to pack the seedlings in short pieces 

 of glass tubing, allowing about 5 millimeters of the root-tip to protrude, then to 

 fasten the pieces of glass tubing to the wooden bars. The pieces of tubing 

 should be arranged so that they lie in a tangential plane. 



For short periods of time the supply of moisture will not need to be replenished 

 if the chamber is well saturated before beginning ; in long continued experiments 

 it is best to introduce more water by means of an atomizer every six or eight 

 hours. 



The advantages of such a chamber for use on the klinostat are that in the 

 moist air the roots are freer to respond than in moist sawdust, where the higher 

 rates of rotation invariably cause the sawdust to become packed at the circum- 

 ference of the cylinder ; the seedlings can be easily observed during the progress 

 of the experiment ; it retains its supply of moisture well,^ — I have seen corn seed- 

 lings grow for four days with only the initial supply of moisture ; it can be rotated 

 in any desired plane and at any speed. Howard S. Reed. 



University of Michigan. 



