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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 " ratv-lmmus,'" 

 which in some cases is deposited as a thin peat layer. The humic 



F"iG. I. Nantucket heath with pearly everlasting {Anaphalis 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, i. 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 



