1912] DEUTSCH—TARGIONIA 
493 
Barnes and Lanp (4) as typical for the Marchantiales. The air 
chambers arise by the splitting apart of the superficial cells just 
Fic. 1 
Fic. 2 
Fics. 1, 2.—Fig. 1, median longitudinal section through the apical cell; fig. 2, 
section in horizontal plane of thallus through the apical cell. 
back of the growing point (fig. 3). However, in the other Mar- 
chantiales described, this splitting originates in an angle between 
the epidermal and hypodermal layers of cells, and proceeds outward 
toward the surface; in Targionia the pro- 
cess is reversed, the cracking apart starting 
at the surface between two epidermal cells 
and proceeding inward. Subsequent divi- 
sions enlarge the space thus formed, as well 
as the breadth of the roof. 
Early in its development the pore is 
closed by rapid divisions in the roof cells, 
and it remains closed until the chamber 
has almost reached maturity. The chloro- 
phyllose filaments develop comparatively 
early in the history of the chamber (figs. 
4-6); as soon as the chamber is 3-5 cells 
broad, the cells of the floor begin to project 
-as papillae. These papillae are divided by 
Fic. 3.—Nearly median 
section through growing 
point, showing origin of 
air chambers. 
transverse walls into filaments, which at maturity are 2-6 cells in 
length. They branch profusely, and in the mature chamber very 
