THE BRYOPHYTA 



213 



Different sexes are borne on different plants. The female organ 

 consists of a number of simple ovaries (Oogonia) (Fig. 592, c; Fig. 593, 

 og), grouped together in a Conceptacle. Each oogonium contains eight 

 Oospheres. These oospheres are set free and are fertilized by motile 

 Gametes, the Antherozoids, which are produced in conceptacles of 

 another plant. 



The Lichens. — IMost systematists now regard the Lichens as belonging 

 to the Fungi. They may be defined as Fungi parasitic on certain 

 Algae. In this form of parasitism each plant supplies some indispen- 

 sable contribution to the other, the relation being therefore called Sym- 

 biosis. The body of the Lichen, more particularly in the larger forms, 

 is made up of the Fungus mycelium (Fig. 595, sh). The thallus may 



Fig. 594. General view of several Lichens: A, criistaceous (Graphis) ; B, a portion of this sameliclien 

 more highly magnified, showing apothecia; C, a erustaceous lichen, Pertusaria; D, a sub-foliaceous 

 thallus of Parmelia with numerous spore-bearing bodies, apothecia. (Sachs.) 



be large and flat, leathery and leaf -like (foliaceous. Fig. 594, D), or 

 upright and branching (fruticose), or close-clinging to the bark of 

 trees, looking like a colored stain on rocks (erustaceous. Fig. 594, A, C). 

 In most cases the spores are born^ eight together, in little sacs called 

 Asci, which are themselves reproduced in variously colored closed or 

 open Apothecia (Fig. 594, D). 



The Bryophyta. — In this class the conspicuous generation is the 

 gametophyte which, in the higher divisions (left hand, Fig. 59G), 

 becomes a well-developed plant with stem and leaves. Its male repro- 

 ductive organs are the Antheridia (Fig. 597, a); its female are the 

 Archegonia. The effect of reproduction is the production of an embryo, 

 which immediately germinates while upon the gametophyte, sending 

 its foot down into the tissue of the latter, and developing upward into 



