376 



SCIENCE 



[N. S. Vol. XLII. No. 1081 



Previous experiments had shown that it was 

 possible to use pollen from flower buds which 

 had been gathered when just ready to open 

 and kept in cold storage until needed, but after 

 five to seven days the buds discolored and 

 moulded. Pollen had been sent in this way 

 from Florida to California, but for a long 

 period of time such as the duration of the 

 Toyage from Florida to Japan, it was neces- 

 sary to develop other methods. 



The attempt was first made to brush the 

 pollen- from the anthers into small vials, but 

 this process was abandoned for the much 

 ■quicker method of putting the anthers entire 

 into the vials. The preparation of the pollen 

 may be divided into four methods, as follows: 

 I., pollen in cork-stoppered vial; H., anthers 

 in vial with cotton stopper; III., anthers in 

 "vacuum glass tubes, i. e., tube filled with 

 anthers for 1-2 inches, cotton i inch, then ex- 

 hausted to about 10 mm. pressure and sealed; 

 IV., anthers in dried vacuum glass tubes, i. e., 

 tube filled with anthers 1-2 inches, cotton J 

 inch, exhausted to about .5 mm. pressure in 

 the presence of sulfuric acid, the tube then 

 sealed. As far as practicable the pollen was 

 kept at a temperature of 10° C. until sealed. 



Through the courtesy of Director Onda of 

 the Imperial Horticultural Experiment Sta- 

 tion at Okitsu, Shidzuoka Ken, Mr. Swingle 

 made arrangements to test the viability of 

 the pollen as well as to make hybrids in the 

 variety collection of citrous fruits. Professor 

 T. Kumagai, of this station, kindly agreed to 

 test the viability of this pollen in 30 per cent. 

 cane sugar solution. His careful observations 

 show conclusively that pollen can be success- 

 fully shipped from Florida %o Japan and be in 

 viable condition on arrival, four to six weeks 

 after it is gathered. 



Grapefruit pollen collected April 6, from 

 one sealed tube (method III.) which was 



2 The sources of pollen were Bowen grapefruit 

 and tangelo twigs bearing flowers fully matured 

 but not yet open, gathered at Eustis and San 

 Mateo, Florida. The lower part of each bundle of 

 stems was packed in moist sphagnum, the bundle 

 then wrapped in oiled paper and mailed from Flor- 

 ida to Washington in ordinary mailing cartons. 



opened May 17, 1915, showed within forty- 

 eight hours a germination of 50 per cent, with 

 the pollen tubes fifteen times the diameter of 

 the pollen grain. Fresh Joppa orange pollen 

 used as a check showed the same germination 

 (50 per cent.) within twenty-four hours, with 

 pollen tubes twenty times the diameter of the 

 pollen grains. Fresh " Ogasawara grapefruit " 

 used as a check showed 80 per cent, germina- 

 tion inside of twenty-four hours, with the 

 pollen tubes twenty times the diameter of the 

 pollen grains. Pollen of Valencia Late 

 oranges used as a check showed a germination 

 of only 20 per cent, within forty-eight hours, 

 and a length of pollen tube of but three to four 

 times the diameter of the pollen grain. Other 

 tubes of grapefruit and tangelo pollen pre- 

 pared in the same manner {i. e., method III.) 

 showed from 2 to 10 per cent, germination, 

 both with pollen tubes from two to five timee 

 the diameter of the pollen grain, while still 

 others gave no results whatever. From obser- 

 vations upon these different lots of pollen it 

 is probable that this may have been due to the 

 pollen having low vitality when gathered. It 

 is obvious, also, that there may be a variation 

 in the viability of pollen of different varieties, 

 or even in pollen from individual flowers. 



Grapefruit pollen sent by methods I. and 

 II. showed 7-8 per cent, germination within 

 forty-eight hours, and pollen tubes ten times 

 the diameter of the grain. 



PoUen prepared by method IV. was sent late 

 in April, so that no report has as yet been re- 

 ceived showing the percentage of germination. 

 However, in a cablegram sent from Tokyo 

 July 8, 1915, Mr. Swingle reports : " Dry 

 pollen successful," indicating that the most 

 promising method for shipment of pollen over 

 long distances is the one last noted, of drying 

 in vacuo over sulfuric acid. 



The necessity for stricter quarantine regu- 

 lations to exclude dangerous diseases and in- ■ 

 sect pests already operates to prevent the free 

 shipment of many plants from one country to 

 another. As such regulations become more 

 strict, the difficulties of securing plants in- 

 crease. It is likely, however, that in most 

 eases pollen shipped in vacuum tubes could be 



