178 BROOKLYN BOTANIC GARDEN MEMOIRS 
an oceanic climate are slight. The relative humidity is higher. There 
is a larger amount of cloudiness and a heavier rainfall than is found 
over continental interiors. Marine climate is equable. With a 
continental climate the annual temperature ranges increase, as a 
whole, with increasing distance from the ocean. The regular diurnal 
ranges are also large. The winters are cold and the summers are hot. 
Cloudless skies are more frequent and the air is dustier and drier. 
In Europe, where heath plants grow, there is a formation of fibrous 
and slightly earthy humous layers, the undecomposed elements of 
which are deposited in dense masses to form the so-called “vaw-humus,” 
which in some cases is deposited as a thin peat layer. The humic 
Fre. 1. Nantucket heath with pearly everlasting (Anaphaiis margarilacea) 
and bayberry (Myrica carolinensis). August 20, 1914. 
acid, according to Ramann, acts on the unweathered silicate, de- 
composing it energetically, bringing into solution alkalis and alkaline 
earths, leaches the soil, 7. e., the soluble substances are carried down 
to greater depths. If raw humus lies on sandy soils, the sand of the 
upper layers appears bleached and becomes light gray in color, being 
in this condition called lead sand. Below this light-colored layer is 
found a yellowish to brownish soil due to the grains of sand being 
mixed with ferric-oxid or ferric hydrate. The precipitated organic 
substances cement the separate sand grains into compacted layers 
