94 
termine the constancy of the characters by which it is separated 
from mucronata forms of M. vestita. These are (a) larger number 
of sori in each valve, (b) greater length of peduncles, (c) uncinate 
' upper tooth of the sporocarp. 
(3) Determine the -degree of fixity of characters in var. 
tenutfolia of M. vestita. No specimens are known to exist ex- 
cept those of Lindheimer and Wright, collected in 1848, and 
these seem to characterize a well-marked variety. The existence 
of a somewhat intermediate type in Reverchon’s specimens 
distributed as MZ. mucronata, and the fact that the original form 
has not been sent in by recent collectors, seem to throw doubt — 
upon the constancy of its characters, as does also the considera- 
tion that all the other distinguishing features insensibly grade 
into mucronata forms of M. vestita ; hence, if it stands, it must 
stand on the basis of the narrow leaflets alone. | . 
(4) \ Observe the relations and the cause of the markings on 
M. picta, Fee, from Mexico. It was claimed by the late Dr. 
Schaffner, who collected Warsilia at San Luis Potosi, that JZ. picta 
was the floating form of his 1. Héltingiana, which we consider 
a depauperate form of I. vestita. Such a marked degree of 
variation would not seem to us impossible, as certain floating 
forms of Jf vestita are as markedly in contrast with the usual. 
forms of that species, if we except the “ pictz ; ” and Dr. Schaff- 
ner claimed that these were produced by infusoria and larve. 
Indeed, we have observed natant forms of JZ guadrifolia in 
Bantam Lake that would present a no less difficult problem to 
the species-maker, if he were to observe them as herbarium speci- 
mens instead of in the field. : 
New Grasses. 
By GEORGE VASEY. 
POA RUPESTRIS. Culms densely tufted, 6 to 9 inches high, 
erect and rigid, striate; cauline leaves (2 or 3) very narrow, erect, 
1 to 1% inches long; ligule conspicuous, membranaceous; 
sheaths smooth, striate; upper part of culm naked; panicle 34 
‘to 1% inches long, narrow, and sparsely flowered; branches 
short, single or in twos below, each with 3 to 5 spikelets, some- 
what expanding in bloom; spikelets about three-flowered, 114 
