Nov. 1904. | BOTANICAL SOCIETY OF EDINBURGH. 15 
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by tyhytyty 
S.—Plankton of Loch Asta. 
This variety differs principally in the scattered disposition of 
the granules, which in typical P. margarttacewm are arranged in 
longitudinal series. 
. Cylindrus (Ehrenb.), Bréb. S.—Lerwick. 
. exiguum, West. O.—Hoy. 
. sptrostriolatum, Barker. O.—Hoy. 
polymorphum, Perty. O.—W. of Kirkwall. S8.—Scalloway ; 
Lerwick. 
cucurbitinum, Biss. O.—Kirkwall; Hoy. S.—Scalloway ; 
Lerwick. 
Forma minor, W. and G.S. West. S.—Lerwick. 
Var. subpolymorphum, Nordst. S.—Lerwick. 
. curtum, Bréb. O.— W. of Kirkwall. S.—Scalloway, Lerwick. 
. minutum (Ralfs), Cleve. S.—Plankton of Loch Beosetter, Bressay. 
Genus CLOSTERIUM, Nitzsch. 
. Cynthia, De Not. S.—Plankton of Loch Trebister. 
costatum, Corda. 0.—Kirkwall. S.—Scalloway ; Lerwick. 
. striolatum, Ehrenb. O.—Hoy. S.—Bressay ; Scalloway. 
untermedium, Ralfs. O.—Kirkwall; Hoy. 
juncidum, Ralfs. S.—Lerwick. 
. macilentum, Bréb. S.—Plankton of Loch Beosetter, Bressay. 
Diane, Ehrenb. 0.—Kirkwall; Hoy. S.—Near Scalloway ; 
Bressay. 
. parvulum, Nag. O.—Hoy; plankton of Loch Kirbister. S.— 
Lerwick ; Scalloway ; plankton of Loch Beosetter, Bressay, and 
of Loch Trebister ; pools in Bressay. 
. Jenneri, Ralfs. S.—Neugles Water ; Bressay. 
tncurvum, Bréb. O.—Hoy. S.—Plankton of Loch Beosetter, 
Bressay, and of Loch Asta ; pools in Bressay. 
Venus, Kiitz. O.—Hoy; Kirkwall; Finstown. S.—Lerwick ; 
plankton of Loch Asta. 
calosporum, Wittr. O.—Hoy ; Kirkwall. S.—Scalloway. 
extle, sp. n. (fig. 10). 
Cl. minutum, cellulis diametro circiter 8-plo longioribus, modice 
curvatum, margine externo gradus arci 80-85 metiens, margine 
interno in parte mediana leviter inflato, apices obtusos versus 
sensim et equaliter attenuatum; pyrenoidibus 2 in chroma- 
tophora unaquaque ; membrana glabra et achroa,. 
Long. 66-70u ; lat. 8°2-8-4y ; lat. apic. cire. 184. S.—In pools, 
Bressay. 
This species differs from Cl. Cornu, Ehrenb., in its smaller size, 
its greater curvature, its tumid inner margin, and in its narrower 
apices. From Cl. tumidum, Johns, it is distinguished by its 
smaller size, its greater curvature, and by its much narrower, 
obtuse apices. 
73. Cl. Leibleinni, Kitz. O—Hoy; Finstown; pond near Kirkwall. 
S.—Lerwick ; plankton of Loch Asta, “Loch Clickhimin, and 
Neugles Water ; Bressay. 
74. Cl. moniliferum (Bory), Ehrenb. S.—Lerwick ; Bressay ; plankton 
of Lochs Asta and Clickhimin, and of Loch Beosetter, Bressay. 
Forma cellulis curvatioribus, apicibus crassioribus. Lat. 61u ; 
lat. apic. cire. 10°5u ; apic. inter se distantibus 275«. 
O.—Loch Kirbister. 
This form occurred in some quantity, and differs from typical 
