QUERIES IN LOCAL TOPOGRAPHICAL BOTANY. 119 
time. In the tract of the Flora of Plymouth, comprising an 
area of twelve miles around the town, it is known to grow only in 
two or three places. In many parts of England it occurs on wall- 
tops, sandy commons, and banks ; so the local circumstances under 
which it appears are suggestive of such queries as, "Why is it so 
rare?" and, "Why, when it does appear, is it exclusively on coast- 
sands?" A nearly allied species — 0. tetrandrum, Curt. — abounds 
with us in the neighbourhood of salt-water, and the rarity of the 
other may possibly be in part due to some of the most suitable 
spots being occupied by the tetrandrum. Such a view would be in 
full accord with the Darwinian doctrine of an especially sharp 
competition between congenerous species. Disciples of this school 
would probably consider it in the south-west of England either as 
a species slowly dying out under the attacks of foes better fitted 
than itself to carry on the struggle for life under existing con- 
ditions, or else as an advancing species with scattered settlements 
in a new tract. That a competition or warfare between species is 
a reality in nature, and not an airy nothing existing only in the 
imagination of theorists, has been strikingly brought before me by 
the great power of increase I have found certain of our wild plants 
to possess when withdrawn from the adverse influences of the 
species around them in their native spots and transplanted to the 
less fully stocked garden flower-border. Of the genus Stellaria 
there is a species — 8. aquatica, Scop. — which occurs in Devon, 
east and north, but fails to extend to its western portions, and is 
altogether unknown in Cornwall. Its places of growth are stream 
sides and damp spots by ditches and drains; so one would have 
thought that the abundant moisture of the extreme south-west 
would have been very congenial to it. It grows in some quantity 
by the Bovey stream on the flat near the village of Chudleigh 
Knighton; but, as if to prove that the very peculiar geological 
features of the Bovey Heathfield are not the cause of its appearing 
there, it shows itself likewise in the parish of Trusham, away from 
the lignite and clays ; and the Eev. W. Moyle Kogers found it last 
year in North Devon. It is not a very conspicuous species, and 
possibly additional stations for it may be found in Mid-Devon; 
but whether so or no, a careful tracing of its line of limit up through 
the county is much to be desired. This plant does not extend to 
Ireland. It seems probable that either species-competition or some 
climatal obstacle has prevented its further westward advance. 
h 2 
