1 66 



MUSCINE& 



thallus ; while in Oxymitra (Bisch.) they are raised above the surface. 



The sporange is a thin-walled spherical capsule, occasionally produced 

 under water, entirely filled with spores without 

 true elaters br columel, and, with its calypter, 

 depressed in the thallus. It is much less differ- 

 entiated in its structure than in the other 

 orders. In all the genera except Riccia and 

 Oxymitra the elaters are represented by sterile 

 cells among the spore-mother-cells. The spo- 

 range bursts irregularly when ripe, but the 

 spores are only set free by the decay of the 



FIG. 147. Sp'i(erocarpus terrestfis Sm. Frond and archegone 

 (magnified). 



FIG. 146. Riella helicophyila 

 Mont, (magnified) 



FIG. 148. Riccia glarica L. A, section of apical region of 

 frond, ar, archegone ; c, oosphere ( x 50). , immature 

 sporogone, sg ; ar, neck of archegone ( x 300). (After Hof- 

 meister.) 



surrounding tissue of the thallus. The spores of Sphaerocarpus (Mich.) 

 and Corsinia (Radd.) have a beautifully sculptured extine. Riella is 

 altogether dioecious, and perfects its fructification beneath the water. 



Principal genera : Riccia (L.), Duriaea (Bor.), Oxymitra (Bisch.), 

 Riella (Mont.), Sphaerocarpus (Mich.), Corsinia (Radd.). 



LITERATURE. 



Kny Pringsheim's Jahrb. wiss. Bot., 1866, p. 364. 

 Leitgeb Die Riccieen, 1879. 



