44 IOWA ACADEMY OF SCIENCE 



The following measurements of the staminal tube of flowers of red 

 clover show that there is considerable variation in length. For this 

 study ten heads were selected, and measurements made of 10 flowers 

 from each; a second group of 30 heads were selected, and measure- 

 ments made of 15 flowers from each head. In all, measurements of 450 

 flowers were made ; the lengths of the tubes were as follows : Least 

 .33 in. (or 8 mm.) ; the greatest .47 in, (or 12 mm.) ; average .385 in. 

 (or 9.4 mm.). The foregoing study shows about the same length of 

 staminal tube as indicated by the figures of Mueller and by Darwin.^'' 



In discussing pollination Knuth says: 



"Self-pollination may also take place when the head of the bee is 

 withdrawn, but Darwin says that this is ineffective (though Kerner is 

 of the opposite opinion) and is rendered inoperative by the previously 

 effected cross-pollination. ' ' 



In some few cases, as indicated by Waldron'^*' clover is self -fertilized. 

 This was accomplished in some cases of hand-rubbing. 



In some experiments made in Ames self-fertalization was accom- 

 plished where the stigma was irritated. This work is being continued. 



It has been claimed by some that clover is fertilized before the flow- 

 ers open. A study of the embryogeny of the clover indicates that such 

 fertilization does not occur. In no case did we find that the egg-cell 

 had been fertilized, in a number of examinations made. 



The experiments of Kirchner indicated self -sterility. Heads en- 

 closed under glass produced no seed. Similar tests, with the same re- 

 sults, were conducted at Ames. 



In July, 1909, Mr. Lyle Clapper, covered many heads of first crop 

 clover; later 495 of these heads were threshed out; no seed had been 

 produced. During the last week in June, 1909, Miss Ada Hayden 

 covered a large number of heads of red clover. These were gathered 

 in August; 76 heads were threshed, no seeds found. Soil, sandy loam. 

 During the middle of August Miss Hayden covered heads of second 

 crop. These were gathered the last week in September and threshed; 

 71 heads produced no seeds; one head contained 2 seeds. Soil, sandy 

 loam. 



During the fall of 1908 and the fall of 1909, many collections of 

 ripened clover heads from different parts of the state were made with 

 the object of determining, if possible, some relation between condi- 

 tions of season and soil and the seed production of the clover. These 



"L. R. "Waldron. Wallace's Farmer, Oct. 21, 1910. 

 "Origin of Species. 6 Ed. 75. (Murray.) 



