148 Rhodora [JuLy 
presence of stomata in the capsule-wall of Ephemerum, their absence 
in Nanomitrium, and a marked difference in the size of the spores, 
which are sometimes 80 y in diameter in Ephemerum but rarely more 
than 35 p in Nanomitrium. 
Nanomitrium Austini was described by Sullivant' from material 
collected by Austin at Closter, New Jersey, in 1865. Later, in 1878, 
Austin found it at Rockland, New York, and these two stations appear 
to have been the only localities known for this minute moss until the 
fall of 1909 when the writer collected it in the town of Hamden, 
Connecticut. The plants there grew on the clayey banks of a ditch 
and were scarcely perceptible without the aid of a lens. These speci- 
mens agree closely with those distributed by Austin) Between N. 
Austini and N. synoicum (James) Lindb., our other native species, 
however, the differences are not great. The spores of N. synoicum 
are said to be more papillose than those of N. Austini, and the leaves 
of the former are often nearly entire, while in the latter they are serrate. 
One of the most striking differences that the writer has noted between 
the two is in their size and habit. In N. Austini the axis of the leafy 
shoot is in most cases very short and the whole plant appears almost 
sessile. In N. synoicum, on the other hand, the axis is often 0.65 
mm. in length, so that the sporophyte with its enveloping cluster of 
leaves is perceptibly raised above the level of the ground. 
The species of Ephemerum appear to be much more widely distrib- 
uted than those of Nanomitrium, yet it is impossible to get any satis- 
factory idea of their range, partly owing to the fact that on account of 
their small size they are seldom collected, but principally because the 
characters which separate the various species are inadequately under- 
stood. For example, in “The Bryophytes of Connecticut” E. serra- 
tum is listed from five stations. The specimens from these various 
localities were determined by five different authorities. Yet upon 
careful examination all five specimens were found to be, not E. serra- 
tum, but E. spinulosum. 
The classification of species in Ephemerum is based primarily on leaf 
characters, and two general groups may be defined. In one group 
are placed those forms in which the leaves do not possess a midrib, 
1 Icones Suppl. 21. pl. 12. 1874. 
? Specimens from this station distributed by Holzinger, Musci Acro. Bor.-Amer. No. 
268. 
3 Musci. Appal. Exsic. No. 45. 1870. 
