82 Rhodora [May 
form of vegetative reproduction, comparable with the gemmae found 
in other genera of the Hepaticae. It is admitted that the presence 
or absence of gemmae in certain cases affords a convenient method 
for distinguishing between closely related species. The gemmi- 
parous habit of Lophozia heterocolpa (Thed.) M. A. Howe, for example, 
makes it possible to separate this species at a glance from L. Muelleri 
(Nees) Dumort., in which gemmae are unknown. If this reasoning 
is applied to caducous leaves (Bruch- or Brutblütter of Correns) 
their presence, if supported by morphological features of even a 
slight character, might well be made the basis for the segregation of 
plants showing this feature from a species in which the leaves are 
clearly persistent. In Schiffner's forma densior of “ Bazzania triangu- 
laris Pears.” and in Müller's var. implexum of Pleuroschisma tri- 
crenatum these conditions are apparently realized. The forms 
designated by these names are clearly identical and differ from 
typical B. tricrenata not only in having caducous leaves but also in 
certain features of the leaves themselves. Instead of being strongly 
convex and narrowing rather abruptly from a broad and rounded or 
subauriculate base, these leaves are plane or only slightly convex 
and taper more gradually from a narrower and scarcely rounded 
base. In connection with the var. ¿mplexum, Boulay! makes the 
interesting observation that it descends from the higher mountains 
into the lower woody zone, while the typical form does not descend 
below the middle woody zone. "lhere is thus a slight difference in 
altitudinal distribution to support the morphological differences. 
If a species of the character just outlined is recognized, the choice 
of a name for it is beset with difficulties. “B. triangularis Pears.” 
should apparently be typified by the forma laxa of Schiffner with 
persistent leaves, but the use of this name in any sense would lead 
to confusion on account of the older B triangularis Lindb. Nees 
von Esenbeck's Herpetium deflecum B impleeum was probably a 
mixture of several forms, but his 8 1 implexum laxius was apparently 
the same as Müller's Pleuroschisma tricrenatum var. implexum. 
Under 8 1 Nees von Esenbeck, as shown above, included Pleuros- 
chisma flaccidum Dumort. as a synonym, and Dumortier’s description? 
certainly agrees with Müller's, except that no mention is made of 
caducous leaves. If it could be established that these were present 
1 Muscinées de la France 2: 50. 1904. 
3 Syll. Jung. 71. 1531. 
