1917] BRIEFER ARTICLES 239 



by removing the knife carrier and all attached thereto from the remain- 

 der of the machine. Gum arabic of medium consistency is used to 

 freeze the objects in. A layer 2-3 mm. thick should be frozen on the 

 chamber before placing the object on for cutting. By this means it is 

 possible to obtain a large number of sections in a very short time, greatly 

 facilitating the study of algae, fungi, and other soft tissues of either 

 plants or animals in which only cell forms and cell relations are being 

 studied. Likewise it is exceedingly useful in preparing cross and 

 longitudinal sections of leaves, soft stems, etc., for class use. It is also 

 inexpensive. One can run the machine 8 hours with no difficulty on 

 40 lbs. of ice. 



In orienting the material for cutting, 2 methods may be followed. 

 Segments of the material may be piled on top of each other on the 

 freezing chamber and covered with gum arabic and frozen. After trim- 

 ming to the desired form the material may then be removed, properly 

 oriented, and quickly refrozen to the chamber. This is desirable only 

 in cases in which the material is too delicate to stand on end or on edge 

 if cross-sections are to be made. In the other method one takes the 

 material, for example, segments of leaves a few millimeters long, dampens 

 them in gum arabic, and piles them one upon another on a knife blade, 

 after which the whole pile is tipped over onto smooth frozen gum on the 

 freezing chamber. With a little care the whole pile may be made to 

 stand on edge and may be frozen in position for cutting cross-sections. 

 N. L. Gardner, University of California. 



