118 JOURNAL OF THE PLYMOUTH INSTITUTION. 
stock, with peculiarities in the maritima gradually developed in a 
succession of individuals through these peculiarities being the more 
profitable under the surrounding conditions. Others, having a belief 
in the fixity of species as such, looking at the two plants, would adopt 
the view of the one being only an extreme variety of the other pro- 
duced by maritime influences; but these would at the same time 
have to acknowledge the power of surrounding conditions to effect 
changes of so great magnitude in the form and appearance of a 
species as to develop it into a variety, having sufficiently distinct 
characteristics to be accounted a species by many well able to form 
an opinion on the matter. Those favourable to the view of a 
metamorphosis of the one kind or the other, evolutionary or 
varietal, would probably each consider their own opinion 
supported by the fact that at a spot in the neighbourhood of 
Plymouth, Saltash Passage, where maritime influences are to some 
extent present but where they must exist in much less force than 
on the open coast, there grows just above the left bank of the 
tidal Tamar a root of Silene, with certain features intermediate 
between those of infiata and maritima, and thus seeming to form 
a link between the two species. Advocates of both the evolutionary 
and the varietal views have, however, to face the fact that what is 
true maritima occurs also at Saltash Passage, and so away from the 
coast, and that after all an explanation of the intermediate features 
of the one root may be found in the doctrine of hybridity. Con- 
sidering the questions now before us, it is somewhat remarkable 
that Darwin, in his Origin of Species (p. 243, ed. 6), should have 
singled out Silene as a genus " in which," to use his own words, 
"the most persevering efforts have failed to produce between 
extremely close species a single hybrid." On the other hand, Dr. 
Forke, in his recent elaborate work on hybrids, gives instances of 
their having been produced between some of the Silene species 1 
(pp. 64, 65). 
Having suggested some queries with regard to the abnormal 
Saltash Passage Silene, I pass on to say a few words about another 
Caryophyllaceous species — Cerastium semidecandrum, L. Its dis- 
tribution needs careful tracing out in Devon and Cornwall; for, 
although accounted a common English species, it would seem to be 
quite rare here, and, as is not the case generally, exclusively mari- 
1 Die Pflanzen, Mischlinge ein beitrag zur Biologie der Gewachse. Berlin, 
1881. 
