102 
F. Cavers. 
the Targioniacese and with the tubular involucre of Monoclea ; 
while the umbrella-like outgrowth of Corsinia represents, so to 
speak, a belated attempt at the formation of the stalked archegonio- 
phore, or carpocephalum, of the Marchantiaceae (Marchantioideae), 
which arises in advance of the archegonia and carries them up with 
it owing to basal growth and also turns them upside-down owing to 
growth of its expanded upper portion. 
Targioniacete. 
This order contains the two genera Targionia and Cyathodium. 
The development of both was worked out by Leitgeb ; further 
investigations have been made on Targionia by Campbell (1), 
Macfadden (15), Cavers (3), and Douin (7), and on Cyathodium by 
Lang (13). The chief distinguishing features of the order are the 
Fig. 11. Targionia hypophylla. A, a plant, seen from above, with male 
branches at the sides and an involucre at the apex ; B, a similar plant in side 
view, showing the bivalved involucre ; C, part of the epidermis, with an air- 
pore in surface view. 
restriction of the antheridia to special short ventral branches of the 
thallus, and the development of an envelope, consisting of two 
lateral scales, around the archegonial group. The latter occupies 
an area immediately behind the growing-point of the thallus, the 
