The Flora of Disko Island and Adjacent Coast of West Greenland. 127 
exist some rather narrow-leaved specimens of L. groenlandicum and some 
broad-leaved ones of L. decumbens. In those cases, however, the absolute 
size of the leaves will be decisive as L. groenlandicum is moreover 
a more large-leaved form. 
By comparing the lists I and II we see that the scanty material 
of L. decumbens from Arctic America and Siberia agrees very well with 
the large one investigated from Greenland. The size and the shape 
of the leaves are nearly the same. And by comparing the lists HI 
and IV, it will be seen that L. groenlandicum from Boreal America has 
somewhat larger leaves than the Greenland specimens, but 
the shape is the same. The American plants belong to the same 
stock, but where growing under more favourable circumstances, they are 
better developed. 
The next question is: Can the plant here called L. decumbens 
by the size and shape of the leaves be distinguished from 
L. palustre of Boreal Europe? By comparing the lists T and IT with 
V we see, that as to the size there is a wide difference: the leaves of 
L. palustre ave on an average twice as long as those of L. decumbens. 
As to shape there seems to be a slight difference too: the leaves of 
L. palustre are also relatively somewhat longer than those of L. decum- 
bens, (Comp. I and V). But as the leaves of plants ranging from boreal 
zones into the arctic ordinarily become smaller, the size of the leaves 
alone would hardly suffice to establish an independent species. 
According to our experience gleaned from the various parts of 
West Greenland, L. decumbens also varies, according to the conditions 
of the habitat, developing rather large leaves in favourable situations. 
Numerous examples will be found in the list I. And, on the other hand, 
it will be evident from examples in the list V that also L. palustre, 
under unfavourable conditions, varies inversely, leaves growing smaller. 
However, even under extreme conditions, the two species will retain a 
certain habit of their own, hardly to be described. After having closed 
my investigation of the whole material | should easily at a glance be 
able to match the different mounted specimens of L. decumbens and 
L. palustre without reading their labels. 
What is f. dilatata Wahl? 
In his Flora Lapponica WAHLENBERG mentions under Ledum pa- 
lustre a 8 dilatatum: “foliis oblongo-ovalibus.” Of this form I have seen 
the following specimens: 
N 1 b I/b 
Sweden, Halunsskiartmany iy ree teins etree 6 27 (6) 3:05 
Japan Nippon alichechonoskitner::)- iri 5 27.5 6.0 4.58 
Lapland, Karesuando, Lastadius...... Pee err Bie 6 40.0 5.8 6.90 
