MARCHANTIACEAE. 



453 



1. Marchantia polymorpha 



L. Marchantia. (Fig. 498.) 

 Thallus deep green, often 

 darker in the median portion, 

 mostly 5"-10" broad and 2-8' 

 long, flat or slightly furrowed, 

 sinuate along the margin. Ven- 

 tral scales hyaline or pale 

 brownish, in three longitudinal 

 rows on each side of the middle, 

 those of the innermost row with 

 cordate appendages, the others 

 without appendages ; antheridial 

 receptacle with eight short 

 rounded lobes; carpocephalum- 

 deeply lobed, the lobes mostly 

 nine, cylindrical on account of 

 the revolute margins; spores 

 spherical, 10-12 ix in diameter, 

 yellow, densely and minutely 

 papillose; elaters usually with 

 two yellow bands of thicken- 

 ing; gemmae-conceptacles with 

 a lobed margin, the lobes 

 spinose-ciliate. 



On walls and on moist soil. 

 A cosmopolitan species, known in Bermuda from a single collection made by Miss 

 L. DeP. Haynes. 



Order 2. JUNGERMANNIALES. 



Gametophyte a prostrate, strap-shaped, dorsiventral thallus or more 

 or less clearly differentiated into stem and leaves, showing slight tissue 

 differentiation, destitute of air-spaces. Rhizoids all with smooth walls. 

 Antheridia in deep depressions or superficial and usually protected by 

 scales or leaves, sometimes scattered, sometimes grouped together in more 

 or less definite receptacles or androecia. Archegonia superficial but usually 

 more or less protected by scales or leaves. Sporophyte differentiated into 

 capsule, stalk, and foot, the capsule splitting irregularly at maturity or 

 more commonly into four equal valves; elaters always present. 



Gametophyte always a thallus (in Bermuda genera) ; archegonia not terminal and 



often not stopping the growth of the archegonial branch. 



Fam. 1. Metzgeriaceae. 

 Gametophyte diflferentiated into stem and leaves ; 



archegonia terminal and stopping the growth of the 



archegonial branch. Fam. 2. .Tungermanniaceae. 



Family 1. METZGERIACEAE. 



Metzgeria Faimily. 



Thallus with lateral or ventral branches or apparently dichotomous, 

 composed of similar cells throughout or with a distinct median strand 

 of elongated cells. Antheridia borne on the upper surface of ordinary 

 thallus-branches or of short, more or less specialized branches, situated 

 in depressions or superficial, in the latter case often protected by scales. 



