On the Morphology of Cyathodium 1 . 
BY 
WILLIAM H. LANG, M.B., D.Sc., 
Lecturer in Botany at Queen Margaret College, Glasgow University. 
With Plates XXI and XXII. 
O UR knowledge of the structure and development of Cyathodium is 
perhaps more obviously deficient than that regarding any other 
genus of the Marchantiaceae. Apart from systematic descriptions 2 , which 
deal with the structural features of mature plants as displayed in herbarium 
material, the only considerable detailed description of its morphology is 
that given by Leitgeb 3 , and his observations appear to have been done upon 
imperfect and probably dry material. Subsequent observers 4 have supple- 
mented this by references to its vegetative structure, based on better 
preserved material, but there is a complete lack of information as to the 
development of the sexual organs and of the sporogonium. It has even 
remained uncertain whether Leitgeb’s suggestion, that the antheridium 
differs from that of all other Archegoniatae in being a stalked unicellular 
structure, is correct or not. 
The interest attaching to the study of this small genus of Liverworts 
is dependent not merely upon obtaining additional data for phylogenetic 
comparison, but upon the biological peculiarities of the plants composing it. 
The structure of the thallus in the majority of the Marchantiaceae may be 
regarded as adapted to life in exposed situations. The intake of water 
is limited to special regions of the thallus, and the system of air-chambers, 
communicating by definite air-pores with the external atmosphere, is such 
1 The expenses of collecting the material for this work were met by a grant of the Royal 
Society. 
2 Cf. Stephani, Species Hepaticarum, vol. i, p. 62, for a full diagnosis of the genus and species 
and for references to the original descriptions. 
3 Untersuchungen liber die Lebermoose, Heft 6, p. 136, Taf. XI. 
* Ruge, Beitr. z. Kenntniss d. Vegetationsorgane d. Lebermoose, Flora, 1893, p. 279; 
Stahl, Ueber bunte Laubblatter, Ann. Jard. Burt., 1896, p. 137, note on p. 201 ; Kamerling, Zur 
Biol, und Phys. der Marchantiaceen, Jena, 1897 ; Andreas, Ueber d. Bau d. Wand u. d. Oeffnungs- 
weise d. Lebermoossporogons, Floia, 1899. 
[Annals ol Botany, Vol. XIX. No. LXXV. July, 1905.] 
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