178 PITTONIA. 
others varietal, has now become accumulated in the herbaria. 
This gathering in of many different plants under one specific 
name is a natural result of easy methods of procedure. It 
is much more easy to unite and combine forms than to dis- 
tinguish them. And then, when the diagnostic characters 
of two related species are plain, it is often next to impossible 
io determine to which species the old name really belongs. 
Such considerations as these may have led botanists to con- 
tinue treating as one, two species easily distinguishable by 
character. 
But I doubt if any one since De Candolle!, in 1836, has 
made a careful and thorough investigation as to the type of 
Linneus’ E. hyssopifolium. A year ago I went over the bib- 
liographic ground of the species, reaching only partially 
satisfactory conclusions. A recent repetition of that study, 
with more herbarium material at hand, has convinced me 
that even Linnzus had two species under the name; in 
other words, that the two figures cited by him as represent- 
ing E. hyssopifolium are figures of two species; that the plate 
of Dillenius is the one answering to Linnseus' description of 
the species, while that of Plukenet was in all probability 
taken from the plant long afterwards named E. linearifolium 
by De Candolle. And I now observe that De Candolle ap- 
pears to have been brought to the like conclusion; for he 
nowhere cites Plukenet's figure, but leaves E. hyssopifolium, 
Linn., as identical with the plant of Dillenius only. 
The most essential feature of the species, as defined by 
Linneeus, is the triple-nerved character of all the leaves, even 
the uppermost and most reduced of them, as the Dillenian 
figure shows. But very little of what is now in the herbaria 
of American botanists under the name shows anything of 
the triple-nerved character; but in one form, namely, that 
to which Dr. Gray at last assigned the varietal name lacinia- 
tum, all the leaves, whether of stem, branches or branchlets, 
are distinctly three-nerved. Moreover, the upper leaves in , 
! Prodr. v. 177. 
