ii MUSCINEsE HEPATICJE M ARCH AN TI ALES 69 



pletely during the long rainless summer, and revive imme- 

 diately with the advent of the autumn rains. In these species, 

 the growing point of the thallus, with a good deal of the 

 adjacent tissue, survives, and at once becomes fresh and active. 

 The scales and mucilage-cells found about the apex are doubt- 

 less water conservers, and according to Cavers (3, 6, 7), the 

 tuberculate rhizoids are also concerned in holding water. In 

 Fimbriaria Calif ornica, even the young anther idia survive the 

 long summer drought. 



It has been shown (Cavers (6, 7)), that the large hyaline 

 cells terminating the green assimilating filaments in the air- 

 chambers of such forms as Conocephalus and Targionia are the 

 principal agents in the transpiration of water from the under- 

 lying tissues. 



Besides the formation of definite gemmae like those of 

 Marchantia and Lunularia, the thallus in most Marchantiaceae 

 is capable of extensive regeneration, even from small frag- 

 ments. In Conocephalus there have also been found tuberous 

 outgrowths, which are formed under certain conditions and 

 are doubtless for propagation (Cavers (6)). 



The Marchantiaceae are readily separable into two sub- 

 families, the Targionieae, and the Marchantieae. Leitgeb 

 has made a further division of the latter family, but some of 

 the characters given are not sufficiently constant to warrant 

 his division, and for that reason it has been thought best not 

 to accept them. Thus Fimbriaria California, which is, in 

 regard to its fructification, typical, has the female receptacle 

 of the composite type, a character which, according to Leitgeb. 

 not only does not belong to the genus Fimbriaria, but is not 

 found in any genus of the group (Operculatae) to which he 

 assigns it. This species too does not have the capsule opercu- 

 late, but opens irregularly. 



The Targionieae include the two genera Targionia, which 

 has been already described at length, and Cyathodium (Leitgeb 

 (7), vi., p. 136), whose development is not sufficiently known 

 to make its systematic position quite certain. In the position 

 of the sexual organs, and the formation of the two-valved 

 involucre about the fruit, as well as the position of the latter, it 

 corresponds closely to Targionia, but the structure of the thallus 

 is extraordinarily simple, there being practically but two layers 

 of cells with large irregular air-chambers between. While two 



