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 



no. iv.-Marchantia: && 162 ) This arrangement of cells 

 rhombic areas on up- containing chloroplasts exposed in air- 

 ^rfTctou^iine^li"- chambers that communicate freely 



chambers), each one through 

 pierced by an air- 

 pore After SACHS, air-pores 



suggests 



the same general mechan- 

 ism for plant work as that B 

 described for leaves, with 

 their internal atmosphere 

 and stomata (13). 



A remarkable fact con- 

 nected with the Marchantia 

 body, as contrasted with 

 that of the Thallophytes, 

 is that it produces no 

 spores. However, provi- 

 sion for rapid multiplica- FIG 163 ,_ Marchantia: A , thallus bear- 



tion is made by the pro- ing little cups containing reproduc- 



, . tive bodies, and an antheridial branch 



auction ot peculiar repro- ^^ its d i sk) as we ii a s some very 



ductive bodies that are young antheridial branches; B, section 



through antheridial disk, showing the 

 developed in little CUpS O11 sunken antheridia. After KNY. 



