tion is available
for the various nut species compared with many other horticultural
plants. The following preliminary experiments were conducted to obtain
data on germination media, forcing methods, and storage conditions for
Corylus and Juglans Sieboldiana pollen. The former was mostly from
hybrid plants produced by crossing the Rush filbert (Corylus americana)
with European varieties.

_The optimum temperature and sugar concentration for germination of
Corylus pollen._

The cut ends of Corylus branches with mature catkins collected March 1,
1942 were immersed in water and forced into shedding pollen in a room at
a temperature of approximately 20 deg. centigrade. The collected pollen was
sifted upon the surface of a thin layer of sugar-agar in petri dishes.

Commercial cane sugar was used in preference to purified sucrose,
because other studies have shown it to contain impurities which
stimulate pollen germination. A range in sugar concentration from 5% to
55% by weight in 5% intervals was made up in distilled water containing
1.5% agar, heated to boiling and poured into the petri dishes.

The pollen was incubated at 10 deg. C. and at 25 deg. C. on the agar medium for
48 and 24 hours respectively prior to making the germination counts.
Pollen was assumed to have germinated if the length of the pollen tube
exceeded the diameter of the pollen grain.

At 25 deg. C. germination was prompt and uniform with a maximum of 19.5% at
25% sugar concentration. At 10 deg. C. the rate of germination was very slow
and incomplete at the end of 48 hours with a maximum of 9% germination
at 35% sugar concentration. For subsequent work a temperature of 25 deg. C.
and a sugar concentration of 25% by weight was taken as a standard.

_The effect of temperature and humidity during forcing on the viability
of the pollen_

Pollen shed from catkins forced in a warm, dry room (about 75 deg. F.), and
in a cool, humid greenhouse (60 deg. F.) gave pollen germinating 36% and 69%
respectively, which indicated that the air temperature and humidity
surrounding the developing catkins may have considerable effect on the
viability of the maturing pollen.

The experiment was repeated by forcing the catkins at 10 deg. C., 18-20 deg. C.,
and 24-26 deg. C., at two humidity levels. The low humidity level
corresponded to the natural room humidity, about 25% and the higher
level of nearly 100% was achieved by enclosing the branches with catkins
in la