1 ] '2 BRITISH PESMTDIACE.E. 



++ Poles rounded and inflated. 



37. Cl. Balntacarenge. 



38. Cl. Scoticum. 

 +++ Poles obtusely rounded. 



39. Cl. pusilbiiii. 



40. Cl. monotsenium. 



y. Cells narrow and elongate ; apices attenuate, acute 

 and generally incurved. 

 Poles slightly recurved, 



41. Cl. prxlongum. 

 ^% Poles incurved. 



42. Cl. sirifjosv in . 



43. Cl. gracile. 



44. CL Lundellii. 



ft Cell -wall striated. 



a. Curvature regular; poles suddenly attenuated. 



45. Cl. attenuatiiDi. 

 /3. Poles slightly recurved. 



46. CL turgid-um. 



47. Cl. Pritchardianum. 



*** Ceils slightly curved ; poles very much attenuated, acute, 



subacute, or rounded. 

 t Cell-wall smooth. 



. Cells almost straight, much elongated. 



48. CL pronum. 



49. Cl. aciculare. 



ft. Cells more or less distinctly curved (rarely 

 straight), relatively shorter. 



50. CL ceratinm. 



51. CL acutiitit. 

 5*2. CL subulatum. 



53. CL idiosporum. 



tt Cell-wall striated. 



a. Median portion of cells not (or rarely) ventricose; 

 poles incurved. 



54. Cl. lineatum. 



|3. Median portion of cells ventricose ; gradually 

 attentiated to the poles. 



55. Cl.Ralfsii. 



56. Cl. decorum. 



57. Cl. laterals. 



y. Median portion of cells ventricose; suddenly 

 attenuated into elongate poles. 



58. Cl. Kiitzingii. 



59. Cl. rostratum. 



60. Cl. setaceum. 



