NOTES ON SALIX LONGIPES. 45 
If the Wardi species were thus restricted only to the 
smooth form, most of the material that has come under 
my observation would: be excluded. The writer has ex- 
pressed elsewhere * his inappreciation of the value of 
pubescence as a character, in respect to another species of 
willow. 
Endeavoring to arrive at the idea of the specific differ- 
ence between 9. longipes and S. Wardi from the descrip- 
tions hitherto given in so far as correctly represented, one 
is much more impressed by their almost perfect parallelism 
than by their divergence. The upshot has been that local- 
ity alone has been the determining factor in classing a given 
specimen either as Wardi or longipes, because of its collee- 
tion at Washington or in Missouri on the one hand, or at 
more southern points on the other, as if the range were 
too large to be covered by one instead of two species. 
8S. longipes has, like many other willows, considerable 
variation even in the same locality, while some of the more 
widely separated localities enhance the variation still more. 
Andersson, in Monog. Sal., says that S. occidentalis inter- 
grades through forms of S. longipes (f. venulosa and f. 
gongylocarpa) with S. nigra by innumerable intermediates. 
Letting S. occidentalis go as already stated, and confining 
our attention to the interval from longipes to nigra, how 
much of this intergrading should be assigned to variation 
per se and how much to hybridism, it is perhaps impossible 
to determine. Wherever I have had the opportunity to 
observe the growth of these willows in the field, the inter- 
grading can readily be accounted for by the latter mode. 
Possibly the same would hold true of other localities. 
The specimens from N. Carolina approach S. nigra. 
Mr. Bush’s specimens from the Indian Territory, judged 
by the leaf alone, seem affected by the same, but the 
fruiting catkins surpass even the ordinary forms of longipes 
in length. Specimens from Texas plainly show the in- 
* See Art. S. cordata X sericea. Bot. Gaz., p. 394, 1896. 
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