112 CLASSIFICATION OF PLANTS 



cells (elaters) which serve to scatter the spores by hygro- 

 scopic movements. 



268. Order i. The Ricciacea are aquatic or semi-aquatic thalloid forms. 

 The sporophyte remains completely enclosed within the archegonium wall 

 and embedded in the gametophyte thallus. It consists merely of a spher- 

 ical capsule filled with spores. 



269. Order 2. The Marchantiacea are larger and more complex in 

 structure. The thallus is perforated by pores on the upper side, which 

 open into air chambers. Surrounding and projecting into these chambers 

 are the green assimilatory cells. The deeper lying cells are larger, 

 contain little or no chlorophyll and serve for water storage and con- 

 duction. The antheridia and archegonia are borne on stalked re- 

 ceptacles. The sporophyte is a stalked capsule which remains attached 

 to the receptacle but projects beyond the old archegonium wall. 



270. Order 3. The Anthocerotaceae are a smaller group. The game- 

 tophyte is irregular thalloid. Its cells contain each a single chloroplast. 

 The archegonia are embedded in the thallus. The sporophyte projects 

 beyond the thallus because of its greatly elongated form, but is not stalked. 

 The capsule splits longitudinally and there is a slender axial "columella" 

 of sterile tissue. 



271. Order 4. The Jungermanniacece are usually differentiated into 

 a stem and dorso- vent rally arranged leaves one cell layer thick. The 

 capsule is long stalked and usually opens longitudinally by four valves. 

 There is no columella. 



272. Order 5. The Calobryacece are represented only by two exotic 

 genera. 



273. Class 2. Musci. The moss plant is differentiated 

 into stem and leaves. There are no true roots but at the base 

 of the stem are found branching rhizoids by which water is 

 absorbed. The stem sometimes contains an axial strand of 

 elongated cells which serve for the conduction of fluids, but 

 there are no true nbro-vascular bundles. The leaves are usually 

 one cell layer thick and are arranged spirally on the stem. 



274. The archegonia and antheridia are borne at the apex 

 of the stem or on lateral branches. The sporophyte is stalked 

 and remains attached to the gametophyte by a prolongation 



