COLOLEJEUNEA MACOUNII 171 
divisions of a bifid underleaf, the other having become obsolete. 
Stephani calls attention to the improbability of this view. Asa 
matter of fact the postical segments cut off from the apical cell 
bear no appendages whatever except the rhizoids. The stylus, on 
the other hand, arises from a lateral segment which normally 
bears a leaf, and there seems to be no reason why it should not be 
considered homologous with the stylus of /rw//ania, which is ac- 
knowledged to be a part of the leaf. 
In a note sent by Spruce to Underwood, it is stated that a few 
stems of the European Cololejeunea Rosettiana (Massal.) Schiffn. 
occur mixed with Hep. Amer. 51. Apparently on the strength 
of this statement, Underwood has listed the species as an Amer- 
ican plant. In the two sets of Hep. Amer. examined by the 
writer, no. 51, which grew on trees, is made up entirely of C. 
Biddlecomiae ; and since C. Rossettiana has not been collected in 
Europe except on calcareous rocks, perhaps it would be well to 
omit it from our lists until its presence is more definitely proved. 
C. Rossettiana was first recoganized in Italy, but has since been 
detected on the British Isles and i western France. It often 
grows in company with C. calcarea, with which it was long con- 
fused. It differs from this species in its broader and even rougher 
lobe and in its plane lobule, which is denticulate on the margin 
and rough on the postical surface. Its stylus also is reduced to a 
unicellular papilla, which is often difficult to demonstrate. 
22. Cololejeunea Macounii (Spruce) 
PLATE 22, Fics. 1-8 
Lejeunea (Cololejeunea) Macounii Spruce; Underwood, Bull. 
Torrey Club, 17: 259. 1890 
Pale green or yellowish, scattered or loosely depressed caespi- 
tose : stems prostrate, 0.08 mm. in diameter, irregularly pinnately 
branched : rhizoids not abundant : leaves imbricated, the lobes sub- 
erect to obliquely spreading, straight or slightly falcate, plane, ob- 
long-obovate, on robust plants 0.7 mm. long and 0.45 mm. wide, 
long, 0.2 mm. wide, keel arched, free margin usually plane and 
