200 JJIiJTISH DESMIDIACE.S. 



West & U. S. West, Alga-fl. Yorks. 19<>o. p. 5S ; Al\ N. Ireland, 1902, 



p. 2!). 



I>nri/liiini Kli i-<'nl>si-<iit var. I "milt nut Turn. Froshw. Alg. E. India, 1S93, 



P. :',i, t. 4, f. 4. 

 D. quantillum Turn., 1. c., 1893, p. 2S, t. 2, f. 9 ; t. 4, f. 12. 



Colls of medium size, rather narrow and subcylindri- 

 cal, 15-20 times longer than their diameter; semicells 

 somewhat variableiu form,notat all or sometimes slightly 

 attenuated from base to apex, with a distinct though 

 small basal inflation and one undulation (sometimes 

 two) immediately above it; apices truncate, bordered 

 by a ring of conical or rounded tubercles, 7-10 in 

 number (4 or 5 visible across the apex) ; cell-wall 

 punctate. 



Zygospore globose or ellipsoid-globose, smooth. 



Length 240-480 //, ; breadth at base of semicells 

 18-oO/x,, at middle of semicells 16-26/x, at apices 

 14-5-22 /x, ; diam. zygosp. 70-90 ^. 



ENGLAND. Cumberland ! Westmoreland! (7iW/x). 

 W., N., and E. Yorks ! Lancashire ! Leicester (Roy). 

 Essex! Cambridge! Oxford! Warwick (JIV//*). 

 Gloucester (CW.-<?). Middlesex (O>o/,r). Surrey 

 (zygosp. from Thursley Common) ! Sussex (Rolfs). 

 Hants! (Raffs). Devon! Cornwall! (Ralf#). 



WALKS. General! (at 2,200 ft. on Glyder Fad), 

 Carnarvonshire) . 



SCOTLAND. General ! (R<>i/ $ Ttixxrtt). Common in 

 Outer Hebrides ! Orkneys ! Shetlands ! 

 ). General and abundant! 

 Distribution.- -France. Germany. Austria 

 and (italicia. Hungary. Italy. Norway. Denmark. 

 Bornholm. Poland. N. Eussia. Nova Zembla. 

 Siberia. Central China. India. Ceylon. Java. 

 Sumatra, Samoa, Australia. New Zealand. Mada- 

 gascar. E. & W. Africa. United States. Brazil. 

 Patagonia. 



PL Ehrenbergii is the most frequent of the British species 

 of tlic pMius, and it exhibits considerable variability in both 

 form nnd si/e. The semicells ;nv i^cncnilly slig-htly ntienu- 

 iilcd I I'om the base to the apex, but in some forms they ;in> 



