A study of the respiration of Xanthium seeds was undertaken some time ago with the purpose of determining whether there was any change in the permeability of the seed coats to oxygen during the period following the normal ripening of the seeds. Some evidence was noted previously that there was either a change in permeability of the seed coat, or a change in oxygen need of the embryo during the early winter, and it was believed that a careful measurement of the oxygen used by the seeds with

more »

... on and off at successive intervals during the year would show which of these changes occurred, and at what period of the ripening process. Circumstances have prevented the carrying out of this series of tests; but the preliminary results are of sufficient interest in connection with the role of oxygen in germination behavior to warrant placing the data on record. The measurements were made with a respirometer of excellent type designed by Dr. WILLIAM CROCKER, to whom I am further indebted for suggestions regarding the problem. The respirometer was kept in a Freas thermostat at 25. 25? C., and the volumes of oxygen used are reduced to standard conditions. Seeds of X. glabratum in dry storage for nine months were used. First it was necessary to know what part of the oxygen was used by the coats under ordinary atmospheric germinative conditions. Two lower seeds were placed in one chamber of the respirometer, and the coats of two lowers in the other chamber. In 22.5 hours the two seeds used 0.475 cc. of oxygen, while the two coats used o. o98 cc. From the results of BECQUEREL'S work2