202 PITTONIA. 
species peculiar to the western slope has grown to be con- 
siderable; and now the following must be proposed in aug- 
~ mentation of the number. 
P. constuitE. Allied to P. Engelmannii, like it in habit, 
but larger, less compactly branching, rather more erect, the 
largest plants a foot high; stems subterete, only the florif- 
erous branches angular, herbage destitute of scurfiness: 
leaves spatulate-linear, the largest 14 inches long, veinless, 
acute, the hardy scabrous margins revolute ; stipules when 
young and untorn bearing 2 or 3 setiform teeth: perianths 
mostly solitary at the nodes (and these more than an inch 
apart as to the lower), much more elongated and narrow 
than in P. Engelmannii, and tightly closed over the achene, 
this with narrowly rhomboid faces and the whole scarcely 
shining, impressed-puncticulate under a strong lens. 
The type specimens of this abundantly distinct relative 
of P. Engelmanni have been lying in my herbarium without 
a name, ever since 1889, and were collected by myself in 
the mountains at Beaver Cafion, Idaho, near the Yellow- 
stone Park, in August of that year. Meanwhile some 
starveling specimens of the same have been collected by A. . 
and E. Nelson in the said Park, and distributed by them 
under the name of P. Engelmannii. In my set of that col- 
lection, the label for these bears the number 6236. 
P. vacans. Also akin to P. Engelmannii, of more spread- 
ing habit, but of the size of the largest P. Douglasii, the long 
tortuous sparse-flowered branches almost prostrate and very 
few, green without any red or purple tinge, subterete, the 
longest more than a foot long, the lower internodes 14 inches 
long: leaves an inch long, spatulatelinear, smooth and 
veinless above but the midyein beneath sharply carinate; 
ocreæ altogether short and obscure: perianths several at 
