jimei6. I9I9 Relation of Weather to Fruilfulness in Plum 125 



(2) Wind has its influence indirectly by interfering with insect action 

 and, hence, pollination at critical times. It is seldom strong enough to 

 cause much direct mechanical injury. The experiments of Waugh show 

 that wind pollination is insufficient, even under the most favorable 

 conditions. Frosts during bloom are only occasional and injure the 

 pistil more than pollen. The greatest damage from low temperatures is 

 in the retarding of pollen-tube growth. Other conditions being favorable, 

 cloudiness does not prevent the setting of fruit. Rain prevents pollen 

 dissemination by closing the anthers or by preventing them from opening, 

 but does not burst pollen nor kill it. 



(3) On account of the adhesive action between stigma and pollen, 

 rain does not completely wash pollen from stigmas. The stigma is 

 receptive for 4 to 6 days, and following the active period of secretion the 

 stigmatic cells rapidly disintegrate. The style abscisses in 8 to 12 days 

 after bloom. Tube growth appears to be relatively slow in the plum 

 even under favorable greenhouse temperatures. As a result of the 

 rapid disintegration in the stigma and the abscission of the style, a delay 

 in pollination or slow tube growth when the temperature is low renders 

 fertilization uncertain. 



(4) An analysis of the prevailing weather at bloom shows that each 

 season certain sets of conditions can be singled out as being largely 

 responsible for the status of the setting of fruit. In one season rain 

 during bloom may be the limiting factor and in another low temperature 

 during the period of tube growth. Unfortunately, practical remedies 

 under orchard conditions do not appear readily available. Late blooming 

 has not escaped unfavorable weather, and, since tube growth seems to 

 be the process most directly affected by low temperatures, remedial 

 measures can most effectively be sought in suitable pollinizers which 

 show the fastest tube growth. 



LITERATURE CITED 

 (i) Backhouse, W. O. 



1912. THE POLUNATioM OF FRUIT TREES. In Gaxd. Qiron., s. 3, V. 52, no. 

 1352, p. 381. 



(2) Ballantyne, a. B. 



i913. blooming periods and yields of fruit in relation to minimum 

 TEMPERATURES. Utah Agr. Exp. Sta. Bui. 128, p. 243-261. 



(3) Beach, S. A., and Fairchild, D. G. 



1893. THE EFFECT OF RAINFALL LTON POLLINATION. NOTE ON PRELIMINARY 



EXPERIMENTS. In N. Y. State Agr. Exp. Sta. nth Ann. Rpt. 1892, 

 p. 607-611. 



(4) GoFF, E. S. 



1894. FLOWERING AND FERTILIZATION OF THE NATIVE PLUM. In Gard. and 



Forest, v. 7, no. 332, p. 262-263. 



(s) 



1901. A STUDY OF CERTAIN CONDITIONS AFFECTING THE SETTING OF FRUITS. 



In Wis. Agr. Exp. Sta. i8th Ann. Rpt. [i90o]'oi, p. 289-303, fig. 61-S0. 



