. Dedication papers : scientific papers presented at the dedication of the laboratory building and plant houses, April 19-21, 1917. ried downto greater depths. If raw humus lies on sandy soils, the sand of theupper layers appears bleached and becomes light gray in color, beingin this condition called lead sand. Below this light-colored layer isfound a yellowish to brownish soil due to the grains of sand beingmixed with ferric-oxid or ferric hydrate. The precipitated organicsubstances cement the separate sand grains into compacted layers HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 179 below th
. Dedication papers : scientific papers presented at the dedication of the laboratory building and plant houses, April 19-21, 1917. ried downto greater depths. If raw humus lies on sandy soils, the sand of theupper layers appears bleached and becomes light gray in color, beingin this condition called lead sand. Below this light-colored layer isfound a yellowish to brownish soil due to the grains of sand beingmixed with ferric-oxid or ferric hydrate. The precipitated organicsubstances cement the separate sand grains into compacted layers HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 179 below the lead sand and meadow ore, and a humus sandstone is is called Ortstein and forms an impervious layer. The roots ofpine trees are unable to penetrate this layer and flatten out on pine trees become stunted, their branches gnarled and the treefinally dies to be replaced by others which pass through the same cycleunless the tap-root manages to pass through a hole into the phytogeographic investigations of the writer have shown thaton the island of Nantucket we have true heaths, called moors by the. Fig. 2. Bear oak {Quercus nana) in heathland, Nantucket. September 7, I9M- inhabitants. Typic heather plants grow on the sandy and gravellyglacial soils of the island and there is a formation of dry peat on thesurface of the soil. The low, rolling hills are covered with plants indifferent groupings, so that in places the western prairies are suggested,while in other places the Roman Campagna, especially where thevegetation has been browsed by cattle. The plain-like character ofthe vegetation is suggested in those areas where the beard grass{Andropogon scoparins) covers the ground in exclusive growth, exceptwhere patches of heath plants are found such as the huckleberry{Gayhissacia resinosa) and the bearberry {Arctoslaphylos uva-iirsi)(Figs. 3 and 4) which forms mats, or carpets of large extent. Anothercommon plant, which suggests the Scotch heather {Callu
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1918
