M archantiales. 
111 
It must be admitted that the habit of the sporogonium, with 
its long seta and its erect cylindrical capsule, differs greatly from 
that of any of the other Marchantiales. Apart from the embryology, 
which is of the Marchantia-type, Monoclea agrees with all known 
Marchantiales and differs from all Jungermanniales (except the 
Calobryaceas) in that the capsule-wall is a single layer of cells in 
thickness (Fig. 17). Moreover, the great length of the seta may 
perhaps he related to the extremely hygrophilous habitat, enabling 
the capsule to he raised well above the wet substratum for the 
dispersal of the spores. In the Marchantiacese, where the sporogonia 
are raised well above the thallus by the stalked archegoniophore, 
there is no necessity for a long seta, and accordingly the latter 
simply elongates sufficiently to thrust the ripe capsule through the 
calyptra. It would appear reasonable to suppose that Monoclea 
represents a blindly-ending line of development arising from forms 
like the Corsiniaceae or the Targioniaceae—a line in which the 
sporogonium itself has assumed the function of thrusting the 
capsule upwards. In the main line of the Marchantiales, which leads 
from these lower forms to the Marchantiaceae, this function has 
devolved upon the outgrowth (archegoniophore) of the thallus which 
carries up the group of fertilised archegonia. 
LITERATURE OF RICCIACEaE, CORSINIACEAE, TARGIONIACEaE, 
MONOCLEACEaE. 
1. Campbell, D. H. “ Mosses and Ferns,” 2nd ed., 1905. 
2. ,, “The Systematic Position of the Genus Monoclea.'’' 
Botanical Gazette, vol. 25, 1898, p. 272. 
3. Cavers, F. “Contributions to the Biology of the Hepaticae. Part I. 
Targionia, Reboulia, Preissia, Monoclea .” Leeds, March, 
1904. 
4. M “ On the Structure and Development of Monoclea Forsten." 
Revue bryologique, 1904, p. 69. 
5 . M “ On the Structure and Biology of Fegatellaconica." Annals of 
Botany, vol. 18, 1904, p. 87. 
6. Coker, W. C. “ Selected Notes. II., Liverworts.” Bot. Gaz., vol. 36, 
1903, p. 225. 
7. Douin, C. “ Targionia hypophylla." Bulletin Soc. Bot. de France, 1906, 
p. 239. 
8 Garber, J. F. “The Life History of Ricciocarpus natans." Bot. Gaz., 
vol. 37, 1904, p. 161. 
7 Gottsche, C. M. “ Ueber das Genus Monoclea." Bot. Zeitung, vol. 16, 
1858. 
10 ,, “ Hepaticae Mexicanae.” Konigl. Dansk. Vid. Sel. 
Skrift., 1867. 
11. Hooker, W. J. “ Musci exotici,” vol. 2, 1820. 
