374 A TEXTBOOK OF GENERAL BOTANY 



ar 
2 
ory 
SSS 
SS 
— SS 
= TaMme 
Siisecti 
aN 
anit 
-, 
Ah 
i 
ATEN 
Fria. 407. Section through an antheridial branch of Marchantia, showing 
air chambers, and also ovoid antheridia containing many sperm cells. (x 30) 
so that the mature spores lie free in the cavity of the enlarged 
archegonium (Fig. 402). The mature sporangium is therefore 

Fig. 408. Young sporophyte of Marchantia 
inclosed within an archegonium 
The tip of the archegonium is disorganizing. 
(x 135) 
nothing more than a mass 
of spores (Fig. 402). The 
sporophyte of the Aveciales 
is the simplest one found 
in the bryophytes. When 
a spore germinates, it pro 
duces a thallus bearing ar- 
chegonia and antheridia. 
ORDER MWARCHANTIALES 
The thallus of this order 
is much more complicated 
(Figs. 403-405) than that 
of the Ricciales. In the 
genus Marchantia, which 
may be taken as an ex- 
ample, the antheridia and 
the archegonia are borne 
on separate plants on spe- 
cial, upright, umbrella-like 
branches. The archegonia 
(Hig. 409) are found on 
