| Racemes | Pods produced | Average number of Plant. | per plant.| by all racemes. | pods to the raceme. ----------+-----------+-----------------+------------------- | | | No. 1 | 84 | 17 | 0.20 No. 2 | 130 | 58 | .44 No. 3 | 166 | 30 | .18 No. 4 | 199 | 88 | .44 No. 5 | 243 | 35 | .27 No. 6 | 131 | 36 | .27 No. 7 | 119 | 13 | .10 No. 8 | 182 | 83 | .45 No. 9 | 340 | 142 | .41 +-----------+-----------------+------------------- Total | 1,594 | 592 | ....... Average | | | .31 ----------+-----------+-----------------+------------------- The results given in Table IV show that an average of 0.31 of a pod to the raceme was obtained from 1,594 racemes and that the variation in seed production of the different plants was from 0.1 to 0.45 to the raceme. The average seed production for the nine plants is 0.11 seed to the raceme less than the average results obtained from the six plants that were covered with cheesecloth. As this difference is well within the limit of variation for individual plants, it may be stated that the shading of the plants in the cheesecloth-covered cages did not reduce the production of seed. The results of this experiment show that spontaneous self-pollination does not occur regularly, as stated by Kirchner. FLOWERS POLLINATED ONLY BY NIGHT-FLYING INSECTS. In order to determine the importance of night-flying insects as pollinators, two cheesecloth-covered cages 3 feet square and 3½ feet high were placed over sweet-clover plants at Arlington on July 10, 1916. The covers of the cages were removed each evening at 7:30 and replaced each morning at 4:30 o'clock. Practically all the flowers on these plants had bloomed by August 2, and the seed produced was nearly mature. The few racemes that contained opened flowers or buds were discarded. The three plants in one cage produced 723 racemes, with an average of 3.76 pods each, while the one plant in the other cage produced 227 racemes, with an average of 3.58 pods to the raceme. The four plants, therefore, produced a total of 950 racemes, with an average of 3.71 pods each. The only night-flying insect found working on sweet clover while these plants were in bloom was _Diacrisia virginica_ Fabr. This experiment was duplicated at Ames in August, 1916, with the result that one plant subject to visitation only by night-flying insects produced 486 racemes, with an average of 16.5 pods each.