424 BOTANICAL GAZETTE. 
aleohol until the soap is dissolved. Add nowa small quantity of 
glycerine. The amount of the latter can be readily ascertaine 
by pouring out a few drops of the warm mixture and allowing it 
Without any glycerine the mass instantly congeals into 
a white friable substance quite unfit for our purpose, but asa pro- 
portion is gradually added the mass hardens less and less rapidly 
and becomes more and more transparent. For soft tissues the 
imbedding mass may be thus made as transparent as. glass and 
exquisite for cutting. For harder substances less glycerine must 
be used. 
With this imbedding material fresh vegetable tissues need no 
preceding preparation, provided there is not a large amount of 
water in them, while substances preserved in alcohol are admir- 
ably adapted for immediate use. If infiltration is desired it is 
only necessary to keep the object some time in the warm mass. 
Tt is clean, and the instruments remain clean. The transparency 
enables one to see clearly the position of the object and to manage 
well the cutting. Thin sections are not so liable to roll up as 
with most other masses. It is readily soluble in water, but not 
in cold aleohol. In cutting it is better to keep the razor and the 
object wetted with the latter and transfer the sections to the 
former. Ifa well tube to imbed in is not at hand, pour the 
melted mass into any convenient dish or paper tray, immerse the 
object, and when the mass cools, cut it out and shape as required. 
Tn cutting let the razor rest flat on the glass top of the micro- 
tome and and hold it firmly with both hands. Make a long draw 
or push stroke, so that a considerable portion of the edge of the 
razor is used each cut. See to it that there is not the least vibration 
of the blade by which the edge may be nicked. If everything is 
in order, and the handling properly done, it is surprising how 
hard substances may be cut without this last occurrence. e 
ought not to be satisfied until we can readily cut sections one- 
thousandth of an inch thick without tearing or bruising. 
GENERAL NOTES. 
Starch Grains.—Starch grains in the cells of potato can be beautifully 
shown by first partially drying the part from which sections are to be made, 
thereby aiding materially the process of cutting. Remove from a fresh tuber 
& prism one-fourth to one-half an inch in diameter and an inch or more ~ 
ength. Expose for a few minutes to moderate heat (hot air from a register 1 
excellent) until the surfaces are quite free from moisture, then allow to remain 
in the ordinary air of the laboratory for twenty-four hours. The consistence 
