240 PITTONIA. 
/ PARTHENIUM STRAMONIUM. Shrub 5 to 12 feet high, 
stout, much branched: leaves ovate-lanceolate, subcordate, 
acute, from almost entire to repand-dentate, green and only 
slightly velvety above, the lower face and the petioles white 
with a fine and close tomentum: coryrmbose panicle rather 
dense and many-flowered, its peduncle and pedicels slender, 
the whole nodding in age. 
No. 393 of Townsend & Barbers’ Chihuahua collection of 
1899; also Hartman's No. 248 from Sonora, this distributed 
as P. tomentosum, which is a plant with much broader and 
coriaceous foliage which is coarsely dentate, and on the 
lower face reticulate-rugose. Its panicle is also stout- 
peduncled and upright. In our plant the leaves in form, 
venation, and arrangement strongly suggest those of some 
species of Datura. 
PickaDENIA DavipsoNi. Biennial, erect, mostly less 
than a foot high, somewhat fastigiately branching, the 
naked peduncles 7 to 15, and 2 to 4 inches long, these and 
the branches striate, hardly at all pubescent: leaves pinnately 
cut into 3 to 7 filiform segments (the basal ones, 7. e, those 
of the first year, not known): heads of middle size for the 
genus; invol broadly panulate, theirovate-lanceolate 
outer braets with notably thickened and indurated base, 
the inner ones longer, thinner, broadly ovate, pubescent: 
achenes densely silky; pales of the pappus ovate, slenderly 
acuminate but not aristate. 
Clifton, Arizona, June, 1900, Dr. A. Davidson. 
V ZYGADENUS LONGUS. Slender, scarcely glaucescent, 2 feet 
high or more, the few and very broadly linear thin leaves 
almost as long as the loosely racemose scape, marked by 
about 11 prominent parallel nerves and as many faint 
