MABCHAXTIACEAE. 449 



on the upper surface of the gametophyte or terminal on more or 

 less differentiated branches. Fertilized egg developing directly 

 into the sporophyte, the wall of the venter of the archegoniuin 

 usually developing into a protective cover, or calyptra, which is 

 not ruptured until the sporophyte is nearly mature. Sporophyte 

 (in all the Bermuda species) differentiated into a capsule (spore- 

 bearing organ), a stalk or a growing region, and a foot (absorbing 

 organ). Capsule consisting of a wall of sterile cells and a spore- 

 sac, the latter sometimes with a median sterile portion (columella), 

 dehiscing irregularly or by means of a lid or of longitudinal splits; 

 spore-sac containing spores only or spores and elaters, the latter 

 consisting of sterile cells often elongated and usually developing 

 spiral bands of thickening on their walls. 



Gametophyte a thallus or leafy shoot. Chloroplasts minute, many in each cell. 

 Capsule short, spherical to oval, without a columella, borne on a translucent 

 stalk. 

 Gametophyte a thick and fleshy thallus, usually pale 

 and differentiated into distinct tissues, rarely 

 deep green and succulent ; green tissue usually 

 with air-spaces. Capsule splitting irregularly 



or by means of a lid. Order 1. March.\nti.\les. 



Gametophyte a delicate thallus or a leafy shoot ; 

 tissue differentiation slight : air-spaces not 

 present. Capsule splitting into four longitudinal 



valves. Order 2. JcNGERii.v.NMALEs. 



Gametophyte a thick and fleshy thallus, dark green 

 and succulent, tissue differentiation slight. Chloro- 

 plasts large, borne singly. Capsule long, cylindrical, 

 with a basal growing region, splitting into two longi- 

 tudinal valves. Order 3. Anthocerot.\les. 



Order 1. MARCHANTIALES. 



Gametophyte a prostrate, strap-shaped, clorsiventral thaUus, growing 

 apically, branching dichotomonsly or from the ventral surface of the 

 median portion, and showing a distinct differentiation into tissues, the 

 green tissue usually with air-spaces. Ventral scales more or less distinct. 

 Rhizoids of two kinds, the one with smooth walls, the other with tuberculate 

 walls. Antheridia in deep depressions on the upper surface of the thallus, 

 sometimes scattered, sometimes grouped together in more or less definite, 

 sessile or stalked, receptacles. Archegonia similar in position but, when 

 borne on stalked receptacles (carpocephala), becoming displaced to the 

 lower surface through intercalary growth. Sporophyte (in all the Ber- 

 muda species) differentiated into capsule, stalk, and foot; elaters (or other 

 sterile cells) usually present in the capsule. 



Family 1. MARCHANTIACEAE. 



Marchantia Family. 



Thallus (except in Dumortiera) with a distinct dorsal layer of air- 

 chambers, communicating with the outside air by means of epidennal 

 pores. Ventral scales in two (or more) longitudinal rows. Antheridia 

 and archegonia borne on more or less definite receptacles; antheridial 



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