410 BOTANICAL GAZETTE. 
J€Ctives, in some cases with one eye-piece, but mostly with two. 
In the matter of objectives there is a range from 1 inch to 4, the 
and 4, § and 1 are also in common use. The high power should 
be of as long working distance as possible. Of course all the 
laboratories have higher powers that can be used as occasion de- 
mands. Several have well emphasized the great advantage of 
providing thoroughly good objectives even for elementary work, 
for nothing can be more discouraging or confusing to a beginner 
than to be asked to try to see with an objective so poor that even 
his instructor could not use it. Professor Spalding urges the use 
of a double nose-piece as a great means of saving time as well as 
wear and tear. In some laboratories eye-piece micrometers are 
used, and in the University of Nebraska these are simple dises of 
thin glass upon which a small scale is ruled, and the disc fastened 
into the tube of the B eye-piece. Such micrometers, when or- 
dered with the instrument, cost about $1.50 each. More labora- 
tories appear to provide stage micrometers, and in some cases one 
micrometer is made to serve the needs of all the students by each 
one making measuring slips of his own. This is very simply 
done by tracing on slips of card-board the micrometer lines 
by means of the camera with every power used. In this 
way every camera drawing can be measured directly. In the 
matter of camera drawing the practice varies considerably. 
Some require it always; others, in addition to its constant use, 
require larger free-hand drawings as better illustrating the 
minor details; others require its use only when exact outlines 
are needed, or when measurements are to be made; others 
teach its use and then leave it optional with the student, one 
still others never use it. but only require free-hand drawing. 
In this wide range of habit the teacher is left to consult his own 
judgment, except that it would at least seem wise for a pupil te 
know ow to use a camera. : 
mple. There is the greatest variation in the matter of sim- 
ple or dissecting microscopes. The idea in all is the same, but 
\ts presentation varies from quite elaborate dissecting instruments, 
costing $10 or $12 each, to home-made affairs, which seem to an- 
“wer every purpose, costing 25 cents to $1 each. In the home- 
made instruments the price depends upon the lens used. At me 
Michigan Agricultural College Coddington lenses are used of 
about + inch focal distance. The wire handle is held by a narrow 
slit in a small post in block of wood about 3 inches long. Sue 
an arrangement will make a good dissecting lens cost about $2.10. 
