126 JOURNAL OF THE PLYMOUTH INSTITUTION. 
of Botany (vol vii. N.S. 16), speaks of the semi-maritime flora of 
that parish appearing to him as its most marked special feature. 
Trusham, although lying on the carboniferous series of slates, as 
well as much of the adjoining parishes of Ashton and Hennock, 
which all produce the angustissimus, is situated near the remark- 
able geological tract of Bovey Heathfield, and I am inclined to 
think the peculiarities in the existing flora of these parishes come 
before us as a record of great geological changes having taken place 
in the locality. 
The multiplicity of the forms and the striking variations seen 
among the Rubi and Rosce make these intricate genera suitable 
for observations having in view the solution of the important and 
much-debated question as to whether an essential difference exists 
between species and varieties, or whether the difference is one of 
degree only. The consideration of the matter might well form the 
subject of a paper for such a society as our own on some other 
occasion. I now pass on to make a few remarks on another very 
important subject, that of hybridism, as it comes before us in the 
genus Epilobium. This genus is represented strongly about Ply- 
mouth, and the abundance of Epilobium lanceolatum, S., is a 
marked feature in the local botany. It occurs in some spots close 
to, or even in, the town, yet so far as the counties of Devon and 
Cornwall are concerned it is a local species ; for there are extensive 
tracts within them from which it is quite absent. As regards 
Great Britain its distribution is very limited ; for of the 112 
counties and vice-counties into which Watson divides the country 
in Topographical Botany, it is given for seven of them only. 
Bearing this in mind, it is certainly a plant whose precise lines of 
extension in Devon and Cornwall should be carefully ascertained 
and exactly recorded. So far as my own observations go it would 
seem to be gradually extending its area. Near Plymouth it is often 
seen growing plentifully on the shelving sides of railway cuttings 
through slaty or shaly rock ; and it has, I suspect, had its more 
general diffusion accelerated by the light beard-appendaged seeds 
having been carried on before passing engines to previously unoc- 
cupied spots. This Epilobium lanceolatum is one of the species that 
frequently crosses with certain others of the genus. Three or four 
often grow intermixed, and this must be favourable for hybridisa- 
tion. The fact that hybridism is known to take place in both the 
vegetable and animal kingdoms has been brought forward by 
