BICKNELL: HAVE WE ENOUGH NEw ENGLAND BLACKBERRIES? 397 
It would need a very keen botanical eye to discover inviolable 
boundary lines separating Rubus allegheniensis from Rubus cana- 
densis on the one hand and from Rubus argutus on the other; and 
between Rubus argutus and Rubus frondosus there exists a range 
of forms equally open to a double claim. Among the trailing . 
species the lines of separation are even less effectively protected. 
There would thus appear to be little room for new species 
in this group. Its units are established at such narrow intervals 
that the organic circumference of each undoubtedly invades that 
of one or more of the others. In es —— genus of plants 
wherein the species move withi ted radius, differences 
far less pronounced than those which mark mere forms or states 
of our Rubi might be evidence enough of distinct organic type. 
The genus Rubus, however, would appear to represent the grow- 
ing point of a genetic phylum subject to great variational activity 
and rapid and impermanent change and, not least to be considered, 
ready hybridization. In this view even wide variations in these 
plants are to be understood as the expression of a concentrated 
phylogenetic energy rather than as evidence of a completed or- 
ganic segregation. 
All of our species, however, show regional and local variations 
which, if unstable, are more or less obvious. For those who enjoy 
the exploitation of varieties here is a pristine field where their name 
islegion. For myself I have never yet been able to comprehend by 
what theory of differentiation the infinite varieties of plants are cast 
into two main categories—the to be named and the to be name- 
less. Not less among the blackberries than in many another 
group the accustomed eye finds varieties well marked for it every- 
where, and moves freely out beyond the range of charted taxonomy 
not to be overtaken by any strained following of printed names. 
Shall we dare to hope, notwithstanding, that the foundations 
builded for this group by our forefathers may not ever be weighted 
by some crataegal structure which it is ill fitted to support? 
It has perhaps been thought that the genus Rubus was subject to 
an interpretation similar to that which has been unfolded in the 
genus Crataegus. To my observation there is an unmistakable 
failure of parallel between the composed and resistent, if often 
slight, differences between the species of Crataegus and the often 
