49 
Sir Joseph Hooker, in his “ Students’ Flora,” Ed. ill. page 8, 
following Dr. Boswell (J. T. Syme, in Eng. Bot., ed. ill.) 
assigns to R. ' proper, prostrate or erect steins 
with straight internodes, and to R. reptans very slender 
creeping stems having arched internodes. The specimens 
of the Ullswater prostrate forms of R. Flammula now before 
you show decidedly arching filiform internodes with creep- 
ing stems ; it was difficult to assign the plants to the one 
species or to the other, and it suggested that a small problem 
in evolution was being worked out under our eyes, and in a 
very restricted area. 
An interesting question which arises is, which of these 
two forms is the primary one ? or are they both modifica- 
tions in two difierent directions of some form which has 
already undergone evolution ? The latter suggestion seems 
the more likely of the two. I^emperature and other climatic 
agencies may be assigned as the chief factors in producing 
these two forms, because the distribution of R. reptans is 
decidedly northern or arctic and sub- arctic, whilst that of 
R. Flammula occurs in its highest development in such 
temperatures as those of our own islands and continental 
Europe. If reptans has been associated with glacial tem- 
perature, and has adapted itself to arctic conditions, it 
accounts for its occurrence in neighbourhoods where glacial 
action is or has been prepotent, and in our own islands 
A¥e may look upon it as a relic of an arctic vegetation, 
most of the members of which have disappeared from our 
flora, or only occur at considerable northern elevations or 
latitudes. The creeping habits of the plant, with its power 
of rooting at every node, and of thus anchoring itself to 
the ground, fit it to hold its own against the fierce blasts of 
arctic regions, and in times of short summers, when its seeds 
could not be brought to maturity, its vegetative organs may 
have preserved it from decimation or extinction. It is not 
a little remarkable that of the two forms, R, reptans per- 
