103 



would furnish new pollen for the earliest bloom of the female 

 trees. 



During the past season of bloom (spring of 1923) the writer, 

 working at Pomona College and at the Government Date Garden 

 at Indio, California, has studied the viability of date pollen by 

 means of direct germination tests. Evidently this is the first 

 time that this method has been employed in the study of date 

 pollen. The results indicate that date pollen does not remain 

 viable from one year to another. 



Four hundred and sixty-four (464) tests were made of twenty- 

 nine (29) different lots of pollen one or more years old that had 

 been carefully dried and stored under the best of conditions 

 employed by date-growers in the Coachella Valley. In each test 

 hundreds and often thousands of pollen grains were used. In 

 all these tests only three germinating pollen grains were found 

 and these were undoubtedly stray grains of new pollen which was 

 being tested in the laboratory at the time. Old pollen that 

 had been kept sealed in vacuum tubes gave no germination. At 

 the same time fresh pollen from good males gave excellent ger- 

 mination. It seems conclusive that pollen one year or more old 

 is unable to grow and is entirely worthless in effecting fertiliza- 

 tion and the setting of fruit. 



The method employed in the test for germination is simple but 

 effective and very reliable. An agar-sugar preparation or 

 "medium" is made, not much different from the "jello" or the 

 "fruit agars" of culinary art. The methods of preparation and 

 sterilization are the same as those used in the common practices of 

 bacteriological research. In preparing for a test of pollen, a tube 

 of the prepared and sterilized medium is heated to the melting 

 point, a drop is placed on a glass slide and as soon as this solid- 

 ifies and is cool the pollen is scattered over the surface. The 

 slide is then placed in a moist chamber for a period of several 

 hours. Many preliminary tests are of course made to determine 

 the kind of sugar and the particular concentration that is most 

 favorable for the growth of the pollen tubes. By this method 

 numerous samples may be tested and the results obtained during 

 a single day's work in the laboratory. 



Date pollen that is viable readily germinates on a i% agar 

 with 3%, 5% or 10% of cane sugar. The pollen tubes make a 

 delicate threadlike growth quite identical to that which grows 



