42 
MITCHELLA, L.—M. repens, L.; common every where in woods; N.Y. — 
OLDENLANDIA, Plumier, L.—0, glomerata, Mchx.; N. Y., O. W. ML; 
Bloomingdale and Brooklyn, State Flora; Closter, not rare, 
Austin. . — 
HOUSTONIA, L.—H. purpurea, L.; New Jersey, Torr. Cat.; Var. longi: 
folia, abundant on Long Island, near Jamaica, Hempstead 
etc.—Il, cerulea, L.; common along Passaic, but does not occur 
near Closter, Austin ; Staten Island. 
VALERIANACE/S. 
VALERIANA, Tourn.—, officinalis, L.; vid. § 52. : 
FEDIA, Geertn.—f, olitoria, Vahl.; cultivated grounds, Inwood, N. ¥., 
W. W. Denslow.—F. radiata, Michx.; fields, Torr. Cat.; is pro- 
bably an error for the former. | 
DIPSACEZ. 
DIPSACUS, Tourn.—D, sylvestris, Mill.; not uncommon; Glen Cove, — 
Coles.—), Fullonum, L.; Orange Co., rare, Austin. 
85. Spirodela.—In reply to a recent communication of specimens, we — 
have received the following letter from Dr. Engelmann. Although — 
he thinks the publication unnecessary, we yet’ venture to print it, 
as he differs from Mr. Austin in relation to the endopleura, and, of : 
course, the subsequent terms of the series. Mr. Austin notified us, 
that he had not had access to his materials for comparison with — 
other species. 
: St. Louis, Nov. 18, 1870. 
Drar Sm: Only to day I finished the examination of your in- : 
teresting Lemna. As Prof. Hegelmeier, the accurate monographer — 
of the family, will no doubt give us a full’description and figure of — 
this plant, from your specimens, I think it superfluous to try to — 
anticipate him in a much less complete and satisfactory manner, — 
a say that, af 4 
ertile fronds are unusually small, onl 23-3}.mm. in 2 
longer diameter, mostly with 5-6 hes or at oes 7; and with 3—5 — 
or sometimes 6 roots. Foliaceous organs ; spiral vessels, (even 12 — 
the roots,) pigment cells, and both forms of crystals, acicular and 1 
glomerate, as in the common form of polyrrhiza ; stomata smaller, — 
only 0.14—0.16 mm. in larger diameter, (whereas in that they are 
fact, Hegelmeige y surmises from Griffiths — 
- coarse but reliable figures of the Indian plant. Pollen grawms — 
: ity, as often elliptical as globose, — 
diameters and sizes; smaller — 
than those of our Lemna paucicostata, (0.023—0.027 mm.) — 
Pistil, as well as anthers and utricle, strongly dotted with purple, 
in alcohol, brown,) subcuticular cells—ovule, hemitropous ; hori 
