104 BIcKNELL: FERNS AND FLOWERING PLANTS OF NANTUCKET 
which, where encouraged by favoring conditions, has produced a 
highly complicated association of individualized forms. 
Nowhere, perhaps, are to be found conditions more apt for 
marked variation and free hybridization in this group of plants 
than on Nantucket. Here, on an outpost island, removed from 
all direct influence of their general tribe, blackberries have for 
centuries grown and spread, acting and interacting under conditions 
of isolation and of group compression which could scarcely have 
failed to register some profound result in their structure and general 
economy. And scarcely in less degree must another influence have 
operated with modifying force in their local status. Within historic 
times the island has undergone almost complete deforestation. 
Subjected to a derangement so fundamental in their environ- 
ment, already closely drawn, this insular group of blackberries 
must have experienced, superadded to their condition of physical 
isolation, a wholly new set of artificial conditions requiring some 
general readjustment of organic contacts among the species 
throughout the group. 
It may be readily conceived that in the case of annual plants, 
or of species perennial by their roots alone, the effect of an environ- — 
ment so specialized and so modified, even though continued for 
a long period of time, might wholly fail to break through the 
organic individuality of old-time species, and thus fail of any 
appreciable expression. But it may be no less readily conceived 
that in the case of a group of plants such as the blackberries, peren- 
nial not alone by the simple root but by suckers as well, and in 
many cases by proliferous and rooting stems, a similar environment 
might well force a response in their morphology, which, once 
elicited, would be effectually shut off from escape. Variations of 
whatever degree in species so constituted would find instant pro- 
tection and ready perpetuation in the mere activities of natural 
growth. An accidental hybrid multiplied by vegetative process 
alone into an established colony would be founded in the strong 
potency of becoming finally widespread. And it is not difficult 
to believe that the establishment of such a new form by vegeta- 
tive reproduction would allow whatsoever period of time might 
be needed to reestablish any impaired capacity of reproduction 
by seed. It is worthy of note that many of these blackberries, 
