June i6, 1919 



Relation of Weather to Fruitjulness in Plum 



III 



and a large part of the water dripping from the tree fell immediately 

 from the stamen cluster. When the style was the same length or shorter 

 than the stamens, the stigma was completely immersed in water. In 

 cases where the style was considerably longer than the stamens, the 

 stigma projected from the drop, especially in positions where the pistils 

 pointed upward. 



During the period of drying after a rain, when the water holding the 

 stamens and pistils is partly evaporated, the anthers break up into 

 groups, each group, however, being still held in water. Gradually, upon 

 further drying, the groups break up, and the anthers assume their normal 

 position in the flower. 



In order to study anther action more in detail at the time of rain, a 

 limb which had been in bloom for three days was cut from a tree during 

 a heavy rain and brought into the laboratory, the temperature of which 

 was about 68° F. All anthers were closed when first brought in, but some 



Fig. I. — An outline drawing of an anther of Minnesota No. 12, showing the adjustment which takes place as 

 a result of taking up or giving off water: A, an anther which has been open in the orchard for three days; 

 B, the same with the anthers pushed up to show the dead area at the upper end of the filament; C, the 

 appearance of the anther after two minutes in water. The anthers are completely closed and have 

 reached their usual size; D, the degree of opening of one suture of the same anthers in 8 minutes when 

 exposed in the laboratory at a temperature of 70° F.; E, the same anther at the end of 12 minutes' drying. 



opened completely in lo minutes under the conditions in the laboratory. 

 When these anthers which had opened were again placed in water they 

 closed in two to three minutes. 



Furthermore, anthers which had been open for approximately 3 days 

 and from which all of the pollen had been shed, when placed in water, 

 closed up and in some trials swelled to the usual size in as short a time 

 as 2 minutes (fig. i ) . Other tests showed that when unopened anthers 

 were kept in water for 2 weeks there was a slight breaking of tissue at the 

 suture but no dehiscence. On the other hand, anthers which had once 

 dehisced and from which the pollen had been shed closed at once when 

 placed in water and remained closed during the 2 weeks of the test. 

 Opened anthers held for 4 days in a saturated atmosphere under a bell jar 

 did not absorb sufficient moisture to close them ; and the experiments of 

 Goflf (5) showed that plum anthers did not open in a saturated atmosphere 

 under a bell jar in 56 hours at a temperature of 65° to 70° F. Goff (5) 

 also showed that in a dry atmosphere low temperatures (about 51° F.) 



