Vol. 15—1961 - NorthEastern Weed Science Society

counted. ThJ grqins m~y ba st~inad by dipo~ng th~ rod int~
Calberla's solution f~r a faw minutss just before counting.
Tests Lnd Lcat e the loss of gr~ins in the ao.l.ut Lon to be slight.
For counting the pollen, tha transparent rods are placed
into 9 contrivance that is gripped by the stage micrometer
and has ad justimerrt s for leveling the surface to be examined.
We are now-,using a further modification: the slide-edgecylinder
sampler. This device utilizes the one milltmeter
edge of a g'l a s s microscope slide for the sampling surface.' The
slide is gripped between two pleno-coRvex rods so its greased
leeding edge forms a portion of a 1/4-inch vertical cylinder.'
After exposure the slide is stored in a standard slide box with
the sample surface up. The sampl~s are counted by placing
two exposed slides in a transparent holder to bring the greased
edges parallel a centimeter apart. They may be stained and
covered with a 22- x 50-mm. cover glass •. The pollen grains
on the 1- x 50-mm. strip are 'easily recognized and count.ed ,
Some other types. of samplers are available that utilize
the principle of collecting on cylinders but either the
accuraa.y of collection or ease of reading the samples leaves
much to be desired. Cylinder samplers are relatively
inexpensive but require a totalizing anemometer for recording
air passage since the efficiency of pollen collection varies
with wind speed~ .
Rotorod
Samplers
The basic sampler was designed by personnel of the
Stanford University Aerosol Laboratory (PerkinsI957). It
has the very great advqntage of being practically independent
of wind speed pnd direction and therefore wind vanes and
anemometer readings ~re not needed. Its major disadvantage is
that it cannot be opernted continuously for a 24-hour day due
to the large volume sampled'lnd consequent overloading of
particles. This sampler collects pollen by impaction on a pair
of small rods whirled through thG air At high speed. The
collecting surface may receive the pollen directly, in which
case the opaque rod is placed on the microscope stage and the '
counts m~de with some difficulty, or the surface may be covered
first with transparent adhesive tape ~llowing the sample to be
removed and affixed to a microscope slide.
This device will overload after two or throQ hours, so
for q 24-hour sample the rotarod unit should h~v~ ~ step-tim0r
to c~us~ the rod to rotAte intermittently. To prevent
impingement of pollen on the rod while stationRry, WJ hAve