HEPATIC^E 



169 



Preissia (Cord.), and the thallus of the latter genus has also rudimentary 

 vascular bundles. The stomates which penetrate the epidermal layer of 

 the upper surface of the thallus into the air-chamber-layer are of a struc- 



FIG. 155.^, B, C, young shoot of M. 



morpha (slightly magnified) with cupules ; 

 . iru, apical region. D, portion of epiderm 



(more highly magnified), sp, stomate. 



FIG. 156. Female inflorescence of M, poly- 

 inorpha seen from the under side, sr, radiat- 

 ing branches ; f, sporogone. (After Goebel.) 



ture quite peculiar to this order. Each stomate is formed, according to 

 Leitgeb, by the simple separation of four or more superficial cells, and the 

 subsequent segmentation of these in a direction parallel to the surface. 



FIG. 157. A, male plant of M. polymorpha. B, longitudinal section through inflorescence, ha 

 o, o, openings to antheridial cavities, a. C, nearly ripe antherid. D, two antherozoids (x 800). 

 (After Goebel.) 



They are situated in the centre of plates of a rhombic form, consisting 

 of portions of the epidermal layer which overarch large air-cavities. 

 From the base and sides of these air-cavities spring chlorophyllous cells 



