434 



BOTANY 



TAUT II 



Tlio wall of the sporogonium possesses stomata, whicli do not occur in other 

 Li^-erworts ; chlorophyll is present in its cells. 



On the under side of the thallus, slit-like openings, formed by the separation 

 of the cells, lead into cavities filled with mucilage. Nostoc filaments jienetrate 

 into these cavities, and develop into endopliytic colonies Q^*). 



Order 4. Jungermanniaeeae 



These are usually small forms which grow on the ground or on tree-trunks, and 

 in the tropics on tlie surface of living leaves. In the simplest forms of tliis order 

 the thallus is hroadly lohed, similar to that of Marchantia {e.g. Fellia epiphylla, 

 frequently found on damp ground) ; or, like that of Biccia fluitans, it is narrow 

 and ribbon-shaped, and at the same time profusely branched {e.g. Mctzgeria 

 furcata. Fig. 112). In the other forms, again, the broad, deeply-lobed thallus has 

 an evident niidril), and its margins, as 



in the case of BJasia pusilla (Fig. 374), ^^/j 



exhibit an incipient segmentation into _^ f 



leaf- like members. The majority of {^^ 



Jungermanniaeeae, however, show a dis- 





J 





Fig. 374. — lUasia 'pusilla. s, Sporogoiiiuin ; 

 /', rliizoids. (x 2.) 



Kio. 375. — PlagiocliUa asplenioicles. 

 Spoi-ogoiiiuiii. (Xat. size.) 



tinct segmentation into a prostrate or ascending, dorsiventral stem and leaves. The 

 latter consist of one layer of cells without a midrib, and are inserted with obliquely 

 directed laminae in two rows on each flank of the stem. Some species {e.g. 

 Frullania Tauiarisci, a delicately branched Liverwort of a brownish colour occur- 

 ring on rocks a)id tree-trunks) have also a ventral row of small scale -like leaves 

 or amphigastria (Fig. 376, «). The dorsal leaves are frequently divided into 

 an upjjer and lower lobe. In species growing in dry places, like Frullania 

 Tamarisci, the lower lobe may be modified into a sac, and serves as a capillary 

 water - reservoir. The leaves regularly overlaji each other; they are then said 

 to be succuhous, when the posterior edges of the leaves are overlapped by the 

 anterior edges of those next below {Frullania, Fig. 376), or incuhous, if the 

 posterior edges of the leaves overlap the anterior edges of the leaves next 

 below {PlagiocliUa, Fig. 375). 



The long-stalked sjiorogonium is also characteristic of this order ; it is already 

 fully develo]icd before it is jiuslicd thi'ough tlie M])ex of the arclicgnnial wall by 



