CHAPTER XI. THE BRYOPHYTA. 



341 



of the most commonly observed species, is illustrated in 



Fig- 549- 



(C) The Marchantiaceae have thalloid, dichotomously 

 branching stems, producing numerous well-developed stomata 

 on the upper surface, and abundant rhizoids and two rows of 

 small scale-like leaves on the lower. The antheridia and arche- 

 gonia are borne in separate, stalked receptacles. The capsules 

 dehisce variously in different species, sometimes by four valves 

 and sometimes irregularly, and the ejection of the spores is 

 aided by spirally-coiled elaters. 



Marchantia polymorpha is found everywhere on damp ground. 

 on wet rocks adjacent to springs and waterfalls, and on the damp 

 earth of green-houses. Fig. 550, A. represents a portion of a 



m 



A B 



Fig. 550. — Marchantia polymorpha. A, portion of thallus bearing a stalked receptacle, 

 a, producing antheridia. B, portion of thallus bearing a stalked receptacle, b, bearing 

 sporogonia on the under surface of the rays: g, one of the receptacles with gemms ; m, 

 one of the gemmae magnified; e, elaters highly magnified, and s, a spore clinging to the 

 elaters. 



thallus, bearing an erect, stalked, wheel-shaped receptacle, a, in 

 the upper surface of which numerous antheridia are imbedded. 

 Fig. 550, i?, represents a portion of a stem of the same species, 

 bearing a female receptacle which consists of a star-shaped body 

 borne at the summit of an erect stalk. On its under surface, 

 near the base of the rays, when the organ is young, are borne 

 the flask-shaped archegonia, and at a later stage, there are 

 developed in their place rounded, short-stalked sporogonia. 

 Sessile, cup-shaped receptacles producing gemmae, small rounded 

 or oblong, cellular bodies, by means of which the plant is 



