In order to obtain information upon the number of flowers that produce seed on the upper and lower portions, respectively, of sweet-clover plants when grown under field conditions and where the stand contained four to five plants to the square foot, a number of racemes were labeled on different portions of the plants at Ames in 1915 and 1916. When the pods were partly mature, records were made of the number of flowers that produced pods. The results obtained are given in Table VI.
Table VI.--_Relation of the position of sweet-clover flowers on the plants to seed production, at Ames, Iowa, in 1915 and 1916._
-----+------------------------+---------+------------------------------ | | | Pods formed. | |Number of+--------+------------+-------- Year.|Position of the flowers.| flowers.| Number.| Percentage.| Average. -----+------------------------+---------+--------+------------+-------- | | | | | 1915 | Upper half of plants | 812 | 357 | 43.9 } | 1916 | do | 261 | 101 | 38.7 } | 42.6 | | | | | 1915 | Lower half of plants | 344 | 44 | 12.7 } | 1916 | do | 216 | 59 | 27.3 } | 18.3 -----+------------------------+---------+--------+------------+--------
The flowers on the upper racemes of the plants produced 31.2 per cent more pods than those on the lower racemes in 1915. and 11.4 per cent more in 1916. These results prove that insects more frequently visit the flowers that are directly exposed and are therefore more accessible.
INFLUENCE OF THE WEATHER AT BLOSSOMING TIME UPON SEED PRODUCTION.
The seed production of sweet clover is seldom satisfactory when rainy or muggy weather prevails during the flowering period. In order to obtain data as to the relation existing between the visits of insects and the prevailing weather conditions, a record of insect visits and of the number of flowers that opened each day was kept for a period of nine days at Ames in August, 1915.
In this experiment the racemes were marked early each morning just above the last flowers which had opened the previous day, and early the following morning the number of flowers which had opened the previous day was noted. The number of flowers that were pollinated was determined by the number of pods that formed. Table VII gives in detail the results obtained.