Igt2] 
DEUTSCH—TARGIONIA 
495 
which in the younger scales overlaps the growing point of the 
thallus, and may serve as a protective covering. The two rows of 
Bei. 
soe 1) S N + 
REGO NH OR 
SR 
Sean cs 
eee 
Be OR) 
SRS tearees 
ie ee 
ae | 
cae 
Cop y 
Se = 
—— 
Fic. 7.—Mature air chamber in median longitudinal section 
scales are separate from the first, 
to the apical cell (CAMPBELL 2). 
Both the pegged and the 
smooth rhizoids are present. 
They are extremely long, and 
most curiously swollen and dis- 
torted at the distal end. Ac- 
cording to CAVERS (3) the 
smooth rhizoids are borne on the 
midrib and pass directly into 
the ground. The pegged rhizoids 
arise in great profusion in the 
axils of the scales and pass back- 
ward along either side of the 
midrib. 
The solid, colorless tissue of 
the thallus is composed of 
elongated and, for the most part, 
highly vacuolate cells. These 
behind the growing point, and 
arising from young segments close 
G. 8.—Transverse section through 
two air chambers, showing their extreme 
arrowness. 
begin their elongation directly 
this process goes on so rapidly 
