PLKI K'oT KNIUM. 



var. n<l iiluximi Hoy, Fmsluv. Alg. Enbrid^e Lake 

 and Vicinity. IS'.iu, p. :53o. 



Plat n>t;i ilium <-<ii'<>iinl nm var. HoduloxH m Wrsl, Ali; 1 . W . Ireland, IS! (2, 

 p. ll'.l; A1-. 1'hi--. Luku Distr. LS'JL', p. 71!); West \ G. S. Wrsl, A1-. S. 

 Kii-laiid, IS 1 .)?, p. 182; G. S. West, Ali^a-fl. Caml.r. !!)!, p. 113 ; \\ . i 

 ^ U. S. West, Algii-tl. Yorks. 1900, p. 5!). 



Semicells with the l);isal inflation slightly reduced 

 and with the apical tubercles much reduced (rarely 

 wanting'). 



Length 835-494 /A; breadth at base of semicells 4o- 

 <)() /a,, at apex 24-41 ^. 



ENGLAND. Westmoreland! (ViW/lv). W. and N. 

 Yorks! Cambridge! Warwick ( Hi/As). Gloucester 

 (Haifa). Surrey! Sussex (Haifa). Hants! Corn- 

 wall ! (Marquand). 



WALES. Capel Curig ! (Coob> <J- II7//.S-), a,nd near 

 Dolbadarn Castle ! , Carnarvonshire. Dolgelly, Merio- 

 neth (Ha] fa). 



SCOTLAND. General ! (Hoy fy Hi-wtt). Outer 

 Hebrides ! Orkneys ! Shetlancls ! 



IRELAND. Cloonee Lough, and 8 miles S. of Ken- 

 mare, Kerry ! Dublin and Wicklow (Archer). Clough, 

 Antrim ! 



Geotjr. Distribution. France. Germany. Galicia 

 in Austria. Hungary. Italy. Norway. Sweden. 

 Bornholm. Central and S. Kussia. India. Central 

 Africa (form). Sandwich Islands. United States. 

 Brazil. 



This is the most abundant and widely distributed of the 

 varieties of Pleurotsenium curuinituiii. It differs little from 

 the type, the most important distinction being the great re- 

 duction in the size of the apical tubercles, but every gradation 

 exists between the condition typical of Pk'iimt^ <n//ini coro- 

 natiini and a form in which the tubercles are completely 

 absent. 



Kabenhorst identifies " Docidium nodulosum Breb." with 

 " Closterium crenulatum Ehreiib.," referring to both under 

 the name of Pleurotsenium crenulatum (Ehreiib.) liubeuli. 

 We do not think, however, that Ehrenberg's " ( '/o.^frrin in 

 crenulatum" is correctly identified with Docidiiou IHH/H/UXH in 

 Breb. Certainly the plants described and figured by Wolle 

 as "Docidium crenulatum" are not identical with Brebi>- 



