THE WINTER STATE OF OUR DUCKWEEDS. 263 
As soon as the cut was made the piece taken off was laid on a 
slide in a drop of glycerine, and the slide numbered ‘* No 1.” Next 
the frond, from which the cut had been made, was put under the 
microscope and the direction and position of the cut observed and 
its place recorded on the camera drawing, and numbered “ 1.” The 
frond was then laid on the finger and the second cut made, as thin 
as possible, and as near parallel to the first as might be. I could 
not succeed in getting the series of cuts as nearly parallel to one 
another in this way, as by cutting all the sections at once without 
removing the razor from its rest against the end of my thumb. 
But generally the deviations from parallelism were not so great as 
to interfere eae with the usefulness of the sections, considered 
as a set. 
After each cut, the section was placed on its separate slide and 
numbered and the remainder of the frond placed under the micro- 
scope and the position of the cut marked. In this way I sometimes 
got a series of fifteen, or twenty sections, extending from one edge 
of the bud to the other. Of these from three to five would pass 
through the budlet. ; 
Next was the study of these sections one after the other in order, 
comparing them with each other, and with the surface view of an 
uncut bud, attempting to construct mentally the complete form of 
which the microscope gave me successive sectional views. I had 
had before just as good sections, in some cases better ones, but 
then could ‘not tell from what part they came and so had been. un- 
able to form a connected satisfactory idea, or model} of the whole. 
One such set shed light in a given direction, but others were 
needed. Some eight sets of vertical sections in various directions 
gave all that could be expected of them, and yet the matter was 
_ hot quite clear. I wanted the budlet sliced in a direction parallel 
with its surface. The plane of the bud is not quite parallel with 
that of the frond, so that I could not get just the right sections by 
the method of splitting the frond between the thumb and fore- 
finger. I could imbed a frond in a mixtyre of gum and glycerine ; 
but that took so long to harden that, if several fronds were prepared 
for cutting, I was very apt to forget just where the cut should be 
made in each, and so run the risk of spoiling the specimen. Some- 
thing was wanted that would set and harden in a few minutes. I 
thought of collodion, and on trial it proved to be just what was 
wanted. When the specimens are saturated with glycerine, and 
