Hesperaster nudus (Pursh) Cockerell and its Allies 
By GEORGE E. OsSTERHOUT 
There are four species of Hesperaster (Mentzelia) found on the 
plains and in the mountains of Colorado which have large white 
flowers. They are all véspertine as to the time of blooming. The 
largest flowered one is Hesperaster decapetalus (Sims) Cockerell 
(Mentzelia decapetala Urb. & Gil.). The size of the flowers so dis- 
tinguish it that it is not likely to be mistaken for any of the 
others. JF. Rusbyt (Wooton) Cockerell (Mentzelia Rusbyt was 
described by Professor E. O. Wooton in the Bulletin of the 
Torrey Botanical Club, 25: 261. This is a large plant having the 
upper leaves sessile by a broad base and acuminate. The flowers 
are smaller than those of the other species and the capsule only 
slightly foliose at base. It surely is not an annual as Professor 
Wooton suggests but seems to be about as enduring as the other 
species, 
There are yet two species which have usually been referred to 
Mentzelia nuda. One of these is strict in manner of growth, 
branching at the middle or toward the summit; the leaves are de- 
cidedly hispid on both surfaces; the capsule has pinnatifid bracts 
at its base, is foliose at base, and the seeds are subovate. It grows 
on the plains. The other is a more branching plant; the leaves 
are not so hispid on the upper surface, the capsule is vot foliose 
at base ; the seeds are round and wing-margined. 
Which of these, if either, is the Bartonia nuda Pursh? Some 
help may be had in solving the problem from the early descrip- 
tions. Nuttall says of Bartonia nuda, “capsule naked.” This 
fact contrasted it with his Bartonia ornata (7. e., H. decapetalus) 
which has the “base of the capsule foliose,” and probably sug- 
ested the name xuda. The description in Torrey and Gray's 
Flora is drawn from that of Nuttall and adds nothing of notes. 
But there is a specimen of Nuttall’s plant yet in the herbarium of 
the Philadelphia Academy of Sciences, and the name Partonia 
vuda is in Nuttall’s handwriting. I am greatly indebted to Mr. 
Alex. MacElwee for comparing specimens with Nuttall’s plant 
and for facts concerning it. 
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