MARYLAND WEATHER- SERVICE 89 



The occurrence of these species east of the Blue Pudge only along 

 the Potomac may well be accounted for by the transport of seeds by 

 the river. 



The Mountain Zone. 



An inspection of the ranges outside Maryland of the twenty-nine 

 species already mentioned as confined to the Mountain Zone shows 

 eight of them to be confined to the Alleghany mountains, ranging 

 from New York or Pennsylvania south to North Carolina or Georgia. 

 These are: Clintonia umbellulata, Cimicifuga americana, Anemone 

 trifolia, Bicuculla eximia, Saxifraga micraniliidifolia, Azalea lutea, 

 MLenziesia pilosa and Solidago monticola. 



The remaining number of Mountain Zone species range in the 

 North from Newfoundland, Nova Scotia or Ontario west to Michi- 

 gan, Minnesota or Manitoba, or indeed as far as Alaska in the case 

 of Strcpiopus roseus and Comus canadensis. Of the total number of 

 Mountain Zone species the southern limit of range in the Alleghanies 

 is as follows : 14 south to Georgia, 7 to North Carolina, 1 to Vir- 

 ginia, 7 to Maryland. The species finding their southern limit in 

 Maryland are the following: Larix larlcina, Alnus incana, Coptis 

 trifolia, Dalibarda repens, Comus canadensis, Gentiana linearis and 

 Lonicera ciliata. 



The most conspicuous habitat confined to the Mountain Zone is 

 the swamp forest, which finds its typical development in the narrow 

 mountain valleys with insufficient longitudinal slope to effect ready 

 drainage. In and about these swamps are found a number of the 

 typically northern forms, for example Picea mariana, Larix laricina. 

 Comus canadensis, Dalibarda repens, Gentiana linearis, and Coptis 

 trifolia. The predominance of Picea mariana and Pinus strobus 

 along streams, in swamps and on the rich soil of flood plains and 

 glades is of considerable interest in connection with the absence from 

 the Mountain Zone of such common species characteristic of similar 

 habitats in the Midland and Coastal Zones as Ulmus americana, 

 Ulmus fulca, Platanus occidentalis and Acer saccharinum. 



