104 



from them into and through the tissues of the pistil to function 

 in fertiHzation. With the use of a microscope giving 75 to 100 

 diameters magnification the individual tubes may easily be ob- 

 served and the percentage of germination may be detennined. 

 The use of appropriate stains facilitates this study. 



A case of excellent germination is shown in the upper half of 

 PLATE 290 with a magnification of 90 times. Nearly every pollen 

 grain in this sample of fresh but dry {)ollen produced a tube 

 which made a vigorous growth. In the lower half of plate 290 

 is a view of pollen one year old submitted to the same test but 

 showing no germination whatever. When pollen grains one 

 year or more old are placed on the agar-sugar preparation they 

 absorb water, swell up, and become plump and well rounded out, 

 but they have thus far exhibited no signs of growth and life. 

 They appear to be dead. 



It is perhaps possible that old pollen may germinate on the 

 stigmas of the female date flowers even when it does not do so on 

 the medium which gives successful germination of new pollen. 

 But the very decided differences observed in the tests — the excel- 

 lent germinations repeatedly obtained from new pollen in con- 

 trast to complete failures of old pollen to germinate — make 

 this unlikelw 



Inquiries among growers reveal that man\- of them mix the 

 first of the new i)ollen of a season with old pollen kept from the 

 previous year. The results of using such pollen do not constitute 

 a test of efficiency of the old pollen, for even thus diluted a super- 

 abundance of the new pollen is no doubt often used. In the in- 

 stances when old pollen has been used exclusively, there has 

 evidently been no adequately guarded pollination which would 

 exclude any new pollen that might be carried in the air from 

 male trees that were in bloom or that might soon come into 

 bloom, either in the same plantation or elsewhere in the region. 

 The very light and minute pollen of the date palm is no doubt 

 widely disseminated by movements of air. Date growers fre- 

 quently get a good set of fruit from clusters of flowers left to open 

 without attention. 



One manager of a date plantation in the Coachclla Valley re- 

 ports tlecidedly i>oor results when he has used old pollen for the 

 pollination of earl\' blooms of female trees. Another grower sa>'s 

 that the results ha\e made him somewhat "suspicious of old pol- 



