CHAPTER III 



MARCHANTIE^ 



Comparing the Marchantieae with the Ricciaceae, the close 

 similarity in the structure and development of the thallus is at 

 once apparent, but the former are more highly developed in all 

 respects. The development of definite air-chambers in the 

 green tissue, and a continuous epidermis with the characteristic 

 pores, is common to all of them with the exception of the 

 peculiar genus Duniortiera, where the development of the air- 

 chambers is partially or completely suppressed. The genera 

 Ricciocarpus and Tessalina on the one hand, and Corsinia and 

 Boschia on the other, connect perfectly Riccia with the higher 

 Marchantiaceae as regards the structure of air-spaces and 

 epidermis, as they do in other respects. The epidermal pores 

 in the Marchantieae are sometimes simple pores surrounded by 

 more or less symmetrically arranged guard cells (Fig. lo, D), 

 or they are, especially upon the female receptacles, of a most 

 peculiar cylindrical form, which arises by a series of transverse 

 walls in the primary guard cells (Fig. lo, C). There is a good 

 deal of difference in the character of the air-chambers in 

 different genera. In Rehoulia and Fimbriaria, for instance, they 

 resemble a good deal those of Ricciocarpus, or more or less 

 complete division of the primary chambers being produced by 

 the formation of diaphragms or laminae, which give the green 

 tissue an irregular honey-combed appearance, and in these 

 forms there is not a sharp separation of the green tissue from 

 the central colourless tissue. In other genera, Marchantia, 

 Targionia (Fig. 1 6), Conocephalus, the dorsal part of the thallus 

 is occupied by a single layer of very definite air-chambers, each 

 opening at the surface by a single central pore. Seen from the 



