50 THE ALGA-FLORA OF CAMBRIDGESHIRE. 
of almost primeval fen; but even these are far from prolific. The 
small pools on the latter, containing Chara hispida and a reduced 
form of Utricularia vulgaris, yielded some rather striking apesiea 
as also did the pools and peaty ditches on Wicken Fen containing 
Utricularia vulgaris and Nymphea alba. The strange appearance of 
Cosmarium anceps, C. angustatum, and C, Holmiense at Chippenham 
is worthy of mention, these species being as a rule entirely confined 
to upland or subalpine districts, being a marked feature of the 
dripping carboniferous grits and shales of the Pennine Chain and of 
similar situations among the older rocks of the Lake District, North 
Wales, &c. ey are notably absent from the south-eastern 
counties of England, and to them may be added C. speciosum, 
which may be placed in the same category, although it is ‘tou in 
Epping Forest, Essex. Roswell Pits, Ely, was found to be a 
locality “ogee beyond the average, and not a few uncommon 
species were obtained from Dernford Fen, about one mile south of 
Shelford. The chalk districts of the south-east of the county yield 
ase iatigd no alge, and the “seaprnn ditches and drains of the 
localities. Some of these, such as agencies Brebissonsi, 
Closterium striolatum, Pear us granulatus, nape os 
Euastrum binale, Staurastrum margaritaceum, &c., really co 
and widely distributed species throughout the Brjtish hos and i hele 
absence # om Cambridgeshire is therefore all the more noteworthy. 
whole I think the Diatoms may be considered as mode- 
rately coienaoe Gee although most of the upland forms are 
naturally absent, and there is a marked absente - pee belonging 
to the genera Eunotia and Melosira. I say ‘ of the upland 
forms’”’ because there are a few found a : Wooken a Chipp onan! 
such as duhaanthidians flexellum, Eptthenin Argus var. alpestris, 
and Kunotia flexellum var. biceps, ng ch are bree? = in 
—e presi Frigid and Alpine cist N. America, and 
ayas 
* Leighton, The Lichen-flora of Great Britain, 1879, 91. 
