132 Мовтем Р. PoRrSsILD. 
and southwards to New Foundland. By RoBiNson & FERNALD a variety 
dilatatum is stated down to the Mountains of Maine and to the Great 
Lakes. If we are right, that would be a luxuriant form of L.decumbens 
L. groenlandicum is а lowland plant ranging through the Boreal 
parts of the whole North American continent, the American analogon 
to the Eurasiatic L. palustre. Besides Southern Greenland it perhaps 
also enters the Boreal Northwestern parts of Asia (according to LEDE- 
BOUR). 
To Greenland the species of Ledum immigrated in postglacial time. 
L. decumbens probably came from the North, over Smith’ Sound. Its 
area in West Greenland is now widely separated from its main distribu- 
tion in Arctic America, and therefore the immigration probably took 
place during the milder climate of an interglacial period. A much larger 
gap separates the Greenland stock of L. groenlandicum from its con- 
tinual American area. It is one of the numerous representatives of the 
Boreal American Forest-Flora occurring in Southern Greenland, 
the immigration of which to Greenland is still totally enigmatic. 
i 228. Rhododendron lapponicum (L.) Want. 
In rather dry heath and on rock shelves. 
Very common throughout the whole area. 
Widely distributed in Greenland, without southern limit, in 
the southern parts however scarcer (Ros.); the northern limit not known, 
but is to be searched for north of 76°. 
Ranging from the shore line to considerable altitudes. 
Early flowering and abundantly fructificating. 
Not much varying; ordinarily prostrate, in the southern parts 
in sheltered positions forms like erect shrubs or dwarf trees occur. 
Covered by snow during winter, but not by thick layers. 
1 229. Loiseleuria procumbens (L.) Desv. 
"On sunny spots in heath, on cliffs, sometimes on fell-fields. 
Common throughout the gneissic parts, scarce on basalt, often ab- 
sent over wide areas here. (Comp. Ledum.) 
Widely distributed in West Greenland without southern limit; 
the northern limit still unknown, in East Greenland not north of 67°16’. 
Ascends to great altitudes. 
Abundantly flowering and fruiting. 
Normally covered by snow during winter. 
