Fururre Borantst. 15 
the leaves are flat on the rock, forming a rosette ; the leaves will 
also become more hairy and possibly a darker red; the flowers 
will become more closely set together, very likely more numerous, 
and perhaps smaller. If this plant and its neighbours in the glen 
freely cross with one another, then a new species will not occur, 
because any variation (except such as is immediately due to the 
situation) will be stamped out by crossing with the original species. 
If, however, this plant and others sown beside it cannot cross 
with the ancestral form, these modifications may become heredi- 
tary, and in course of time a new species will arise. The plant is 
really in a sort of island, and we know that in islands there are 
often an enormous number of peculiar or endemic species, and it 
is this absence of crossing with the parent species, combined with 
changed conditions, which has produced them. There are three 
ways, at least, in which this may act in our own country. 
(1) The spot may be an island by position, so that crossing can 
scarcely occur. Hence the importance of studying localities. 
The Hieracium nitidum of Backhouse discovered by J. T. John- 
stone in 1892 at Andrewswhinnie, could only, by an inconceivably 
minute chance, be crossed with its parent. (2) It may be an 
island through change in the flowering period. If the plant on 
the exposed spot blooms and finishes flowering before its relatives 
in the glen begin to flower it cannot be crossed with the parent. 
Hence the importance of knowing how long a plant remains in 
flower, and when it begins and ceases blooming. (3) It may be an 
island through its insect visitors being different. It is obvious that 
if the same insect does not occur in both places, crossing is im- 
possible, and hence the importance of insect visitors. 
I trust that in the preceding I have shown that the future 
British botanist will have plenty to do, and I give it as my 
deliberate impression both that this study of the zy and ow is 
the most important of all botanical enquiries, and also that any 
person who chooses can make the most valuable discoveries by 
careful observation in his own back garden. 1 could certainly 
have expanded this paper to many times its present length, but I 
forbear, trusting that some of these hints may induce others to 
follow this fascmating enquiry. 
