CRYPTOGAMS 



199 



become separate individuals. The plant is attached to the 

 ground by absorptive hairs, or rhizoids. Above, the sur- 



B 



334. Marchantia : A, thallus with rhizoids (r), cupules (c), and archegonial 

 branch (6) ; B, section of archegonium, the fertilized egg (e) having 

 divided once; C, disk of fruiting branch cut to show sporogonia 

 (m, n, o) ; D, opened sporogonium with enveloping sheath (pe), and 

 remains of old archegonium (ar). 



face is seen on close inspection to be divided into small, 



slightly raised areas, each with a pore at the summit. 



The pore leads into a chamber (Fig. 335), from the floor of 



which rise short fila- 



ments or rows of richly 



chlorophyllous cells 



the chief assimilatory 



tissue. This arrange- 



ment has the same ef- 



fect as that of the loose 



tissues in the leaf of 



Flowering Plants (see 



Fig. 382), where pores (stomates) give free passage to gases, 



while the epidermal covering retains moisture, 



335. Section in upper part of thallus to 

 show P re <P) and assimilating cells 



