1924} Wiegand,—Some Changes in Nomenclature 3 
Dewey’s plant had long peduncles but short spikes, and the plant 
was said to be prostrate. Our plant is a tall robust form of C. hysteri- 
cina with ordinary peduncles but long pistillate spikes. 
Potyconum MUHLENBERGII (Meisn. Watson, forma natans, 
forma nov.—Caulibus submersis elongatis natantibus; foliis natanti- 
bus glabris lucidis. 
Stems elongated, rooted at base, submerged, floating above; leaves 
floating, glabrous, glossy. Some specimens examined are: Massa- 
CHUSETTS: Lake Cochituate, Natick, 1908, K. M. Wiegand & M. 
Heatley. New York: Hermon, O. P. Phelps, no. 1550. Coronapo: 
Fort Logan, 1915, P. A. Munz, no. 26. WASHINGTON: Moscow, 
1913, W. C. Muenscher, no. 129 (Tyre in Herb. New York State 
College of Agriculture.) It occurs occasionally through central New 
York. 
This form bears the same relation to typical P. Muhlenbergi that 
the floating form of P. amphibium does to f. terrestre (Leers) Blake 
and f. Hartwrightii (Gray) Blake. It can usually be distinguished 
from P. amphibium by the more acute leaves, longer spikes (3-9 em.) 
and flowers of a deeper pink. 
OENOTHERA PARVIFLORA L., var. angustissima (Gates), var. nov. 
O. angustissima Gates, Ruopora xv. 46 (1913). 
OENOTHERA BIENNIS L., var. nutans (Atkins. & Bart.), var. nov. 
` O. nutans Atkinson & Bartlett, Rnopona xv. 83 (1913). 
OENOTHERA BIENNIS L., var. pycnocarpa (Atkins. & Bart.), var. 
nov. O. pycnocarpa Atkinson & Bartlett, RHopoRA xv. 83 (1913). 
In recent years the writer has given much attention to the “ bien- 
nis" group of Oenothera, both in the field and in the larger herbaria, 
but without very satisfactory results. There seem to be two species 
in the eastern United States of the kind usually understood as species 
by taxonomists. These have been given expression in Gray's Man. 
ed. 7 as O. muricata and O. biennis. 'The two species differ by good 
structural characters, but these are not the characters usually desig- 
nated in our manuals. In the former species the pubescence of the 
foliage, if present, is strigose, the body of the seeds about 1.7 to 2.2 
mm. long and 1.0 to 1.5 mm. broad, and the sepal-tips often subter- 
minal. In O. biennis the leaves are velvety beneath and somewhat 
thinner in texture, the seeds 1.2 to 1.8 mm. long and about 0.8 mm. 
broad, and the sepal-tips usually terminal and connivent. All other 
forms with which the writer is familiar are not distinct structurally, 
but intergrade, and the differences are frequently very slight and 
difficult to recognize. The status of the large-flowered forms variously 
called O. Lamarckiana, O. grandiflora, etc., is not clear. They may 
