rOllELLA. 79 



Found on the Continent and in North America. 



Obs. — This, the commonest of our British Radidm, is dis- 

 tinguished from all the others by its paroicous inflorescence. 



The antheridia are normally situated below the young 

 perianth, but with its maturing, they disappear and the bracts 

 assume the form of ordinary leaves ; but a lateral young branch, 

 proceeding from below the perianth, usually bears 3-5 perigonial 

 bracts with an immature perianth at its apex. 



Description of Plate XXVII. — Fig. 1. Plant natural size. 



2. Portion of stem, antical view x 11 (Barmouth, W. H. P.). 



3. Ditto X 16 (ditto). 4. Ditto, postical view x 11 (Dove Dale, 

 W. H. P.). 5. Portion of stem with perianth x 21 (Jack del.). 

 6. Portion of leaf x 290 (Dove Dale, W. H. P.). 7. Perianth 

 with bracts x 11 (ditto). 8. Perigonial bracts x IG (ditto). 

 9. Young flower, showing ? and 3" x 40 (Gottsche del.). 



Subtribe IT. PORELLE/E. 

 Genus 5. PORELLA, mil 



Porella, Dill. Hist. muse. p. 459 (1741) ; Lindb. in Act. soc. sc. fenn. p. 329 (1809). 

 Bellincinia et Antoira, Kaddi Jung. Etr. iu Mem. Moden. xviii. p. 18 et 19 (1820). 

 Cavendishia, Gr. and Benn. Nat. Arr. Brit. PI. i. p. 689 (1821). 

 Madotheca, Dum. Comm. p. 111. (1822). 



Dioicous. Stems regularly pinnate and feather-like ; branches 

 lateral, axillary. Leaves incubous, often subopposite, complicato- 

 bipartite ; postical lobe much smaller, exterior base often decurrent. 

 Stipules large, basal angles decurrent with a laciniate and crispate 

 wing. 



Flowers $ lateral, nearly sessile. Bracts 2-pairs, bilobed, 

 dentate or ciliate. Perianth short, ovate, frontally compressed, 

 trigonous on section, mouth plurilaciniate, at first constricted, 

 afterwards bilabiate or campanulate, Calyptra globose, carnose, 

 rupturing below the apex. Pedicel very short, not projecting 

 beyond the perianth. Capsule globose, pale, membranous, divided 

 nearly to the base into 4 valves. Elaters small, short, bi-trispiral, 

 free, attenuate at both ends. Spores rather large, somewhat 

 angular. Androecia shortly spicate; perigonial bracts exactly 



