168 A TEXT-BOOK OF BOTANY 
epidermis there are several layers of colorless cells; above 
these there is a series of large air-chambers into which 
project the curious cells containing the 
chloroplasts; and forming the dome-like 
roof of each air-chamber is the upper 
epidermis, pierced by a single air-pore 
in the center of the roof of each cham- 
ber. Each air-pore resembles a little 
chimney, built up with several tiers of 
cells. The rhombic areas seen on the 
surface of the body are the outlines of 
the air-chambers, and the minute open- 
ing in the center of each is the air-pore 
(Fig. 162). This arrangement of cells 
Fig 162.— Murchantia: 
rhombic areas on up- containing chloroplasts exposed in air- 
per surface of thallus : 
(surface outline of air- Chambers that communicate freely 
chambers), each one through 
pierced by an. air- fa 
pore.— After Sacus. alr-pores 
suggests 
the same general mechan- 
ism for plant work as that 
described for leaves, with 
their internal atmosphere 
and stomata ($13). 
A remarkable fact con- 
nected with the A/archantia 
body, as contrasted with 
that of the Thallophytes, 
is that it produces no 
spores. However, provi- 
sion for rapid multiplica- 
A é Fic. 163.—AMarchantia: A, thallus bear- 
tion 1s made by the pro- ing little cups containing reproduc- 
Ane f i tive bodies, and an antheridial branch 
uction of pecuhar repro- with its disk, as well as some very 
ductive bodies that are young antheridial branches; B, section 
i . through antheridial disk, showing the 
developed in little cups on sunken antheridia—After Kny. 
