Contributions in geographical exploration . the water is so abundant as to standon the surface. (See page 332). For a long while it was verymuch of a puzzle why it did not spread onto the adjacentground, whose soil-water content is more similar to that ofthe habitats it usually occupies. But finally an explanationsuggested itself because of the similarity of conditions in theseplaces to the alkali spots on the ])rairies. Everyone familiarwith such a region as the Dakota i^rairies has noticed thatsuch springy places become covered by a heavy crust of alkalisalts, left behind from the evaporatio
Contributions in geographical exploration . the water is so abundant as to standon the surface. (See page 332). For a long while it was verymuch of a puzzle why it did not spread onto the adjacentground, whose soil-water content is more similar to that ofthe habitats it usually occupies. But finally an explanationsuggested itself because of the similarity of conditions in theseplaces to the alkali spots on the ])rairies. Everyone familiarwith such a region as the Dakota i^rairies has noticed thatsuch springy places become covered by a heavy crust of alkalisalts, left behind from the evaporation of the seepage places occupied by the plants in question present exactly 332 The Ohio Journal of Science [Vol. XIX, No. 6, similar conditions. Evaporation from the free water surfacemust similarly affect the concentration of salts. The ashcontains such small amounts of the soluble salts necessary forplants that it may be supposed that only where concentratedby evaporation do they occur in amounts sufficient for vigorousgrowth.*. Photograph by Robert F. Griggs CALAMAGROSTIS LANGSDORFII APPEARING IN AN AREA WHERE WATER, COMING TO THE SURFACE, MAY HAVE ITS SALTS CONCENTRATED BY EVAPORATION. Surrounding pumice flats, where the surface is protected from evaporation, are bare. If this reasoning is correct, it would explain the decidedadvantage of the plants in the wettest places over those on thegeneral surface of the ash where the loose top layer, acting as a *Dr. Shipley, in the sixth paper of this series, has reported that the totalsoluble salt content of the ash is in general not especially low. But in analysisdirected particularly toward the solution of this question, Professor C. W. Foulk,found that in the ash at Kodiak the amount of available (i. e., water soluble)potash was only , which is exactly the amount given by Hilgard as theminimum concentration requisite for plant growth. Phosphoric acid was presentin an even smaller amount, which Professor Foulk desc
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