FRESHWATER ALGAAS, 57 
PLATE III. 
Fras. 123-125.—WNostoc disciforme sp. n., young colonies. (123, X 140; 124-125, x 500.) 
Fic. 126.—Nostoe disciforme sp. n., thalli. (Natural size.) 
Fras. 127-180.—WNostoc disciforme sp. n. 127, 128, two filaments ; 127, with spores ; 129, two groups of 
spores ; 130, filament with sheath. (127, 128, 130, x 500; 129, x 700.) 
Fig. 1381.—WNostoe disciforme sp. n., small part of a mature thallus. (x 30.) 
Fig. 132.—WNostoc longstaffi sp. n., thalli. (Natural size.) 
Fires. 183-184.—WNostoc longstaffi sp. n., young colonies. (X 500.) 
Fires. 135-136. 5s 55 ,, filaments with spores. (135, x 700; 136, x 500.) 
1Bive!, WBZ i os », small part of a mature thallus. (x 30.) 
Fig, 138.—WNostoe fuscescens sp. n., thalli. (Natural size.) 
Fia. 139. 5 9% »  ayoung thallus. (x +00.) 
Fias. 140-142. aa » filaments. (140, 142, x 700; 141, x 500.) 
Fries. 143-144. » young thalli. (x 800.) 
Fras. 145-146.—Tolypothrix conglutinata Borzi. 145, a small part of the richly branched filament ; 
146, the end of one of the branches. (x 500.) 
Fria. 147.—Fragilaria curta Van Heurck. (xX 1350.) 
Fras. 148, 149 and 149a.—WMelosira sp., ef. p. 46. (x 1350.) 
Fra. 150.—? Cyclotella operculata Kitz. (x 550.) 
Fre. 151.—Coscinodiscus decipiens Grun. (x 1250.) 
Fras. 152 and 152a.—Diatoma elongatum Ag., var. ehrenbergi (Kiitz.) W. Sm.; 152, girdle-view ; 
152a, valve-view. (152, x 1950; 152a, x 1350.) 
Fra. 153.—Navicula borealis (Ehrb.) Kitz. (x 900.) 
Fras. 154, 155.—Navicula globiceps Greg.; 154, f. amphicephala; 155, f. elongata. (154, x 1250; 
155, x 850.) 
Fias. 156, 157.—Denticula tenuis Kiitz. var. antarctica var. noy. (156, X 1250; 157, x 1500.) 
Fias. 158-160.—Calothrix intricata sp. n.; 158, a typical part of the stratum (the trichomes are only 
shown in two cases) ; 159, 160, single filaments. (158, x 400; 159, x 800; 160, x 500.) 
Fies. 161-163.—Calothriz antarctica sp. n.; 161, 162, filaments showing false branching. (161, 162, 
x 400; 163, x 550.) 
Frias. 164-172.—Calothriz gracilis sp. n. 164, filament showing false branching; 165, 172, typical 
filaments ; 166, 167, base of two filaments, showing inflation; 170, part of a filament 
showing an intercalary heterocyst ; 171, base of filament with a subconical heterocyst. 
(164, 165, x 500 ; 166-169, 171, 172, x 700; 170, x 1200.) 
