Table VIII.—Effect of water upon the seed production of sweet clover when growing under droughty conditions at Ames, Iowa, in 1916.
| Stage of development when labeled. | Plant not watered. | Plant watered. | Increase from watering. | ||
| Number of racemes labeled. | Average number of pods per raceme that matured. | Number of racemes labeled. | Average number of pods per raceme that matured. | ||
| Flowers at the base of the racemes just ready to open. | 49 | 27.39 | 110 | 55.63 | 28.24 |
| Pods 3 to 6 days old | 30 | 21.13 | 112 | 39.81 | 18.68 |
| Pods 9 to 12 days old | 35 | 15.23 | 50 | 29.86 | 14.63 |
The effect of the water was noticeable soon after the first application, as the leaves and flowers on this plant became turgid and the anther sacs burst at the proper stage of their development. Very few flowers fell after the second day. The water decidedly checked the aborting of immature pods, as is shown by the results obtained on the racemes which were labeled after the pods had formed. The racemes which contained pods 3 to 6 days old when labeled matured 9.95 pods to the raceme more than those which contained older pods at the beginning of the experiment, but this was expected, as most of the aborting which caused this difference had taken place before the racemes were labeled. As very few pods aborted before they were 3 to 6 days old, the difference of 9.95 pods to the raceme in favor of the ones labeled when the flowers at their bases were just ready to open was largely due to the dropping of the flowers on the older racemes before the experiment was begun.
It will be seen that the production of mature pods on the plant not watered was much greater on the racemes that were labeled before the flowers opened than on the older racemes. This difference is undoubtedly due to the precipitation which fell on the sixth and tenth days of the experiment. It is believed that the yield of 15.23 pods to the raceme on the ones labeled when the pods were 9 to 12 days old is representative of the production of pods per raceme previous to the precipitation and that the other racemes on this plant would have yielded proportionately if conditions had remained the same.
In the early spring of 1916, Melilotus alba was planted in several large pots in the greenhouse of the Department of Agriculture at Washington, D. C. These pots were placed outside the greenhouse in the late spring, where they remained until the following January, when they were taken into the greenhouse. The plants grew rapidly and began to flower during the latter part of April, 1917. At this time two pots were placed in a large cage made of screen having 20 meshes to the linear inch. One pot was submerged in a tub of water, so that the soil was saturated at all times, while the plant in the other pot was given only sufficient water to keep it from wilting. The pods on a few racemes were self-pollinated and the results obtained are given in Table IX.
Table IX.—Effect of moisture on the seed production of Melilotus alba at Washington, D. C, in 1917.
| Soil treatment. | Total number of-- | Flowers that matured (per cent). | |||
| Racemes. | Flowers. | Pods formed. | Total. | Increase. | |
| Soil given only a limited quantity of water. | 12 | 227 | 65 | 28.63 | ...... |
| Soil saturated. | 17 | 425 | 235 | 55.03 | 26.22 |
The results of this experiment compare favorably with those obtained under field conditions at Ames in 1916.