Page:The Journal of Indian Botany.djvu/174

144 THE JOURNAL OF INDIAN BOTANY. pass over two rockers, or shallow drums, which actuate the glass plate and prism respectively. The plate carrying the instrument is screwed firmly to the tree, and the variation in the position of the bands observed by a small telescope placed a few feet away. By this means hourly growths of 0'00003 to 0'0003 of an inch can be observed ; and measurements made with the instrument, as shown in the diagram for the Oak, Douglas Fir and Black poplar, show that variations in growth are roughly inversely to variations in temperature, the growth being most rapid when the temperature is lowest. The author suggests that this may be due to variations (with temperature) of the rate of evaporation from the leaves coupled with a nearly constant rate of absorption by the roots : and that while the rate of formation of the new wood is represented by the mean line drawn through the diagram of girth, the divergence from this mean represents the degree of turgescence in the bark and the layers immediately underlying it.

The humidity of the air was not observed so the effect of variation in it could not be calculated, but rain had apparently the effect of increasing the girth.

P. F. F.

Stapleton, R. G. : and Adams, Margaret. The Effect of Drying on the Germination of Cereals. The Journal of the Board of Agriculture* XXVI, 4, July 1918, vp. 364—381.

The problem of the life and death of seeds is one that has at various times received considerable attention, but is by no means yet completely solved. Blackmail, Ewart, Demoussy and others have enlightened us on various points, and the writers of the article under review treat from a practical standpoint the effect on germination of the drying of the seeds or cereals.

The process of drying (called " conditioning ") is used by the miller and the maltster to ensure uniform germination. On the same principle, drying was utilized for the further investigation of unsatisfactory samples of some cereal seeds.

The cereals used were wheat, barley, rye and oats.

It was found that sound seed if sown immediately after thrashing, gives a percentage of germination much lower than that obtained if the same seed is dried artificially or kept without special drying for 2-3 weeks. In the case of unsound seed drying or keeping may cause a decrease in germination percentage. Grain that has been harvested or stacked in bad conditions, and grain that has commenced to sprout are such seed.

The drying given was for three days at 40° C after receipt of the sample. The keeping meant that the gain remained in its sample bag for two to three weeks after receipt.

The reviewer would remark that it would seem as if some kind of V ripening " goes on during the drying or keeping period. We may only guess what this may be. It is worth remembering that dry integuments are, impervious to gases, and that the drier the seed the better does it stand high temperatures. All these facts may have some connection.

Demoussy (Comptes Rendus 1916, 162, 435) held that a seed contains not only a miniature plant, but also a mass of microorganisms that compete with the plant for oxygen, and suggested that some method of partial sterilisation would be useful. Has drying .some such effect V

W. Burns.