290 
F. Cavers. 
characters, and the structure of these branches and of the sporo- 
gonium and its envelopes enable us to refer these aberrant genera 
to their systematic position in the group. 
In Metzgeriopsis (Thallolejeunca) pusilla, an epiphyllous plant 
discovered by Goebel (28) in Java and investigated by him and also 
by Schiffner (70), the thalloid plant-body is ribbon-like, branched 
pinnately, and consists of a single layer of cells; each branch grows 
by a two-sided apical cell, as in Metzgeria. Along the margin of 
the thallus there arise appendages arranged in regular order and 
consisting of cell-rows; from their regular succession, these appen¬ 
dages may, perhaps, be regarded, as Goebel points out, as rudi¬ 
mentary leaves. The thallus is fixed to the substratum by rhizoids, 
and it is propagated asexually by gemmae. The plant is dioecious, 
and may bear a considerable number of male or female leafy 
shoots, each of these shoots replacing an ordinary branch. Each 
sexual shoot grows by a three-sided apical cell, which is doubtless 
derived directly from the two-sided apical cell of an ordinary branch, 
and after producing one or two rudimentary leaves it proceeds to 
the development of large well-developed bilobed leaves which 
protect the sexual organs. The male catkin-like branches bear 
about ten perigonial leaves, each saccate at the base and having a 
pair of antheridia in its axil; the female branch has about six leaves, 
the largest two forming the involucre around the perianth. At the 
base of each sexual shoot, rhizoids are usually given off in a tuft. 
In Pteropsiella frondifonuis, discovered by Spruce in Brazil, 
growing on fallen leaves and decaying wood, the vegetative body is 
a strap-like thallus which resembles that of Podomitrium or the 
species belonging to the “ Repentes ” sections of Blyttia and 
Symphyogyna, rather than that of Metzgeria. It has a well-marked 
midrib about six cells thick, and on either side an expanded single¬ 
layered wing. Growth takes place by a three-sided apical cell, each 
lateral segment bearing papillae which come to occupy the margin 
of the wing at regular intervals, while the ventral segments produce 
small simple amphigastria. From the midrib, on the lower side of 
the thallus, there arise sterile thalloid branches and also leafy 
sexual shoots. The male shoot has a stalk-like base continuous 
with the midrib of the thallus, and bears numerous male bracts in 
two lateral rows—the writer (5) has noted that in some cases the 
male shoot may resume vegetative “thalloid” growth after producing 
the antheridia, the apex growing out to form a flattened expansion 
on either side of the mid-rib or stem. The female branch bears a 
