782 REPORT—1904. 
9. On the Reduction of the Marchantiaceous Type in Cyathodium. 
By Wiut1am H. Lane, .B., D.Sc. 
The species of Cyathodium grow in damp, shaded situations in the tropics, and 
exhibit a simplification of structure as compared with other Marchantiacew. A 
detailed examination of C. fectidissimum, a larger, less reduced form, and C. auieo- 
nitens (which agrees closely with C. cavernarum, investigated by Leitgeb) confirms 
the systematic position close to Taryionia usually assigned to the genus. 
As compared with Targionia the species of Cyathodium appear to constitute a 
reduction series, the reduction affecting both the gametopbyte and the sporo- 
gonium. The thallus, as is well known, is greatly reduced in thickness; the 
layer of air-chambers opening by simple pores is retained, but assimilating fila- 
ments are absent from the chambers. Assimilation is mainly performed by the 
cells of the epidermis, which are adapted to utilise the feeble light in the same 
way as the lens-shaped cells of the protonema of Schistosteya. The lower tissue 
of the thallus is for the most part composed of a single layer of cells. C. fartidissi- 
mum has, however, a narrow midrib several cells thick, the cells being inhabite 
‘by an endophytic fungus, The amphigastria are reduced to small scales composed 
of thin-walled cells in C. fetidisstmwm, and to simple rows of cells in the other 
two species. Both smooth and peg rhizoids occur in C. fotidissimum, but in 
C. aureo-nitens all the rhizoids are thin-walled. Branching of the thallus in both 
species occurs dichotomously and by the formation of adventitious branches from 
the lower surface just within the margin. 
The archegonia in C. fetedissimum are produced from the apex of a branch 
which becomes displaced towards the ventral surface. They thus occupy the same 
position as those of Taryionia, and, as in that genus, the displaced margin grows 
up as the involucre, which becomes completed behind by the further growth of the 
apex itself. In C. awreo-nitens the archegonia are found in acropetal succession 
on the upper surface of the apical region of a branch of the thallus. ‘The apex, 
after forming the archegonia, grows on to form the involucre, which is roofed in 
by the limiting layer of the last formed and incomplete air-chamber. The 
development and structure of the archegonium is as in Targionia. 
The antheridia are borne on short disc-shaped adventitious branches, In 
C. feetidissimum an antheridial branch is situated in the middle line below, just 
behind the archegonial group or groups. In C. awieo-nitens the branches are borne 
close to the margin, and usually alternate with the archegonial groups. The 
antheridia completely fill the cavities in which they are sunk singly; each 
antheridium consists of a stalk two or three cells in length, a wall of a single 
layer of large clear cells, and the central group of spermatocytes. 
The first divisions of the fertilised ovum in C. fwtidissimum agree with those 
in Targionia, but in C. aureo-nitens a row of four cells is formed before longitu- 
dinal divisions appear. ‘The mature sporogonium consists of a capsule the wall 
of which is one layer of cells thick, except at the apex, where a definite group of 
thin-walled cells is present, and a short cylindrical foot. The foot in C. fartidissi- 
mum is composed of four rows of cells, in C. awrco-nitens of a single row except 
at the base, where a group of four cells is present. ‘These basal cells, which are 
throughout recognisable by their larger size, grow out in both species into short 
branched processes, which ramify among the surrounding cells; this occurs about 
the time of the division of the spore-mother-cells. Thickening bands are present 
on the cell-walls in the upper third only of the capsule wall in both species. ‘The 
cells of the lower part of the wall in C. fetidissimwmn have their internal walls 
brown, but present no special peculiarity. Those of this region in C, aureo-nitens 
are thin-walled, packed with starch, and have nuclei which are enlarged and of 
abnormal appearance. 
The sporogonium of C. fetidissimum is much smaller than that of Targionia ; 
the spores are smaller than those of the latter, but, like them, are thick-walled. 
The sporogonium of C. aureo-nitens is only about half the length and breadth of 
that of C. fetidissimum, but the spores are few in number and absolutely 
