84 THE AMERICAN MONTHLY [Apr 
them. The pith and primary cortex are also shown. 
CYPERUS LONGUS.—Shows irregular disposition of vas- 
cular bundles in monocotyledonous stem. This arrange- 
ment of bundles is due to the obliquely radial course of 
the leaf-trace bundles, These enter the stem from the 
leaves, run obliquely downwards into the stem, and then 
bend again outwards and approach the surface. A trans- 
verse section may thus pass through different leaf-trace 
bundles at different heights in their course and show 
therefore bundles of different structure and size.—J. R. 
L. Dizon. 
Notes on Microscopy. 
F, SHILLINGTON SCALES, F. R. M. S. 
Watson’s NEw “UNIVERSAL”? CONDENSER.—The faults 
of the ordinary Abbe condenser are, as is well known, 
the imperfection of its spherical and chromatic corrections. 
The former in particular greatly reduces the value of the 
condenser for the critical work. With a numerical ap- 
erture of from 1°2 to 1:4 the aplanatic aperture does not — 
exceed ‘65. There have been several achromatic conden- 
sers upon the market, but their aplanatic cones have but 
slightly exceeded the simpler Abbe form, whilst the 
mounting has been so cumbrous as to frequently interfére 
with the movements of the mechanical stage. Within 
the last year or two there have been put upon the mar- 
ket several condensers of large N. A. and almost equal 
aplanatic aperture, but their powers have been not less 
than 4 inch, with a field accordingly too small to be ad- 
vantageously used with low-power objectives. To Mr. 
Chas. Baker must be given the credit for first putting in 
the hands of microscopists a condenser witha N. A. of 
1:0 and an aplanatic aperture exceeding ‘9, and with a 
power of less than 4d inch. Messrs. Watson & Sons, of 
High Holborn, have just brought out a similar conden- 
