American Species of Marchantia. 



277 



lack them completely, although no specimens have yet been seen 

 in which a careful examination failed to show traces of sclerotic 

 cells in this region. 



The appendages of the ventral scales (Fig. 10) have better 

 developed teeth than in any other North American species of 

 Marchantia J although the South American M. papillata is a close 



Fig. II. Marchantia domingensis Lehm. & Lindenb. 



Epidermal pores of thallus, x 225. A, B. In surface view. C, D. In 

 cross-section. E, F. Inner openings. A, C, E. Texas, F. D. Heald. 

 B, D, F. Cokely, near Castleton, Jamaica, W. Harris. 



rival in this respect. The teeth are very irregular, the simplest 

 being single cells which project as rounded or bluntly pointed pro- 

 cesses. Between these simple teeth and irregular lobes, several 

 cells long and wide, are all possible gradations. The apical tooth 

 tends to be longer than the others, although this tendency 

 is not always apparent. The median cells of the appendages are 

 often longer than broad and a decrease in the size of the cells 



