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._ -------------------------+------------------+---------+--------+-------- |Total number of-- | Flowers that matured | | (per cent). +--------+---------+---------+--------+-------- Soil treatment. | | | Pods | | |Racemes.| Flowers.| formed. | Total. |Increase. -------------------------+--------+---------+---------+--------+-------- | | | | | Soil given only a limited| 12 | 227 | 65 | 28.63 | ...... quantity of water. | | | | | 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. Part II.--STRUCTURE AND CHEMICAL NATURE OF THE SEED COAT AND ITS RELATION TO IMPERMEABLE SEEDS OF SWEET CLOVER.[3] [3] The writers wish to acknowledge the service rendered by Mr. H. S. Doty, Instructor in Botany, Iowa State College, Ames, Iowa, in assisting in the preparation of this article. HISTORICAL SUMMARY.