HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 179 
below the lead sand and meadow ore, and a humus sandstone is formed. 
This is called Ortstein and forms an impervious layer. The roots of 
pine trees are unable to penetrate this layer and flatten out on it. 
The pine trees become stunted, their branches gnarled and the tree 
finally dies to be replaced by others which pass through the same cycle 
unless the tap-root manages to pass through a hole into the subsoil. 
The phytogeographic investigations of the writer have shown that 
on the island of Nantucket we have true heaths, called moors by the 
Fic. 2. Bear oak (Quercus nana) in heathland, Nantucket. September 7, 
1914. 
. inhabitants. Typic heather plants grow on the sandy and gravelly 
glacial soils of the island and there is a formation of dry peat on the 
surface of the soil. The low, rolling hills are covered with plants in 
different groupings, so that in places the western prairies are suggested, 
while in other places the Roman Campagna, especially where the 
vegetation has been browsed by cattle. The plain-like character of 
the vegetation is suggested in those areas where the beard grass 
(Andropogon scoparius) covers the ground in exclusive growth, except 
where patches of heath plants are found such as the huckleberry 
(Gaylussacia resinosa) and the bearberry (Arctostaphylos uva-urst) 
(Figs. 3 and 4) which forms mats, or carpets of large extent. Another 
common plant, which suggests the Scotch heather (Calluna vulgaris), 
