The failure of pollen to germinate in the catkins at 100% humidity suggested the possibility that the catkin tissue might contain some substance which prevented germination of the mature pollen grains until after it was shed. Two mature catkins plus remnants of their unshed pollen were ground in a mortar with a small amount of water in clear quartz sand. One cubic centimeter of the resulting turbid suspension was added to 10 cc. of warm fluid agar and mixed by rotating the petri dish. Pollen which gave a 91% germination on the standard medium showed only 50% germination on this catkin extract. Germination was distinctly abnormal with short stubby pollen tubes, often with numerous nodular swellings. In general the pollen tube grew up into the air away from the surface of the agar, rather than down into it or parallel with the surface as in normal germination. _Storage of Corylus and Juglans Sieboldiana pollen_ Sulphuric acid solutions to give humidities from 10% to 100% in 10% intervals were made up. The storage chambers consisted of Atlas one-pint, wide-mouth fruit jars. In the bottom of each was placed a small 1-oz. bottle containing 20 cc. of the sulphuric acid solution. The pollen was placed in small glass vials loosely stoppered with cotton. Two lots of Corylus pollen of 80-1/2 and 96-1/2 initial viability respectively, and one lot of Juglans Sieboldiana pollen of well over 50% viability were used in the experiment. Storage temperatures of 0 deg. 40 deg. and 10 deg. were used. The Corylus pollen was placed in storage March 20, 1942, and the Juglans April 12, 1942. The pollen was taken out of storage November 28, 1942 and germinated on the standard agar-sugar medium at 25 deg. C. for 24 hours. Results are given in table II. Table II. The effect of storage temperature and humidity on percentage germination of Corylus and Juglans pollen ------------------------------------------------------------------ Kind of Temperature Degrees Per cent relative humidity Pollen Centigrade 10 20 30 40 50 60 70 80 ------------------------------------------------------------------ Corylus 10 deg. 0 0 0 0 0 0 0 -- Juglans -- 0 -- 0 3 0 0 -- Corylus 4 deg. 0 0 0 0 9.0 0 -- 0 Juglans -- 0 -- 0 -- 0 0 0 Corylus 0 deg. 3.0 1.0 4.5 8.5 0 0 0 0 Juglans -- 0 -- 12.0 -- 12.0 0 0 ------------------------------------------------------------------ This preliminary work indicates that Corylus pollen can best be stored at 0 deg. C. at 30 to 40% relative humidity and Juglans pollen at 0 deg. C. at 40 to 60% relative humidity. _Summary_ 1. The optimum sugar concentration for germination of Corylus pollen is around 25% by weight in 1.5 per cent agar at 25 deg. C.