M archantiales. 
io 5 
attributable to their very different habitats. Targionia is xerophilous, 
with well-developed thallus, assimilating filaments, and thick 
epidermis; Cyathodium grows in moist and shaded places and 
shows markedly hygrophilous characters. Lang investigated C. 
foetidissimum (the largest and least reduced species, with well- 
defined air-chambers and with tuberculate as well as smooth- 
walled rhizoids) and C. cavernarum (the most reduced species, with 
less regular air-chambers, no distinct midrib, inconspicuous ventral 
scales, and no thickened rhizoids). The thallus consists for the 
greater part of a single basal layer of cells, upon which are borne 
the air-chambers. The latter contain no filaments, and the thin- 
walled epidermal cells have strongly convex upper and lower walls, 
probably serving as lenses to collect the feeble light in which the 
plant lives. The male branches and the archegonial receptacles 
have much the same structure as in Targionia. The capsule has a 
well-developed apical cap, and the seta consists of only two or four 
rows of cells. For details, reference should be made to Lang’s 
extremely interesting paper (13). 
Monocleace^:. 
The genus Monoclea, of which two species are distinguished by 
systematists (M. Forsteri in New Zealand, M. Gottschei in tropical 
and South America), is one of the most interesting among the 
Hepaticse. The genus was founded by Hooker (11) for a plant 
discovered by Forster during Captain Cook’s famous voyage and 
named by Forster “Anthoceros univalvis.” Hooker showed that 
the plant was no Anthoceros , since its oblong capsule has no 
columella and opens by a single slit, giving it a spoon-like 
appearance. Gottsche (9) described the minute structure of the 
thallus, noting the presence of two kinds of rhizoids (some wide and 
thin-walled, others narrow and thick-walled) and the occurrence of 
fungal hyphze in the lower tissue, the structure of the ripe sporo- 
gonium, the one-layered capsule-wall, and the long spirally thickened 
elaters. Later, Gottsche (10) discovered the oval cushion-like male 
receptacle in plants from Mexico. Leitgeb 1 noted that the thick- 
walled rhizoids are distributed over the whole underside of the 
thallus and lie parallel with it, while the thin-walled ones arise 
only from the thicker middle portion of the thallus and stand out at 
right angles to it. He concluded that Monoclea is more closely 
related to Pellia than to any of the Marchantiaceze, though it 
1 Unters., III., p. 62; VI., p. 130. 
