30 F. E. FRITSCH. 



This Alga, about the determination of which I am not quite certain, formed a 

 stratum together with Phormidium anyustissimum W. and G. S. West. The filaments 

 were very densely and irregularly entangled, and many of them showed a complete 

 spiral coiling of several turns (figs. 74, 75) ; others, however, were merely fiexuous 

 or even straight for a considerable distance, such filaments being on the whole in 

 the majority. The sheath was prominent, mostly fitting very close, although 

 occasionally a little off-standing. The cell-contents were pale blue-green and often 

 vacuolar or provided with scattered granules of moderate size. In no case could a 

 regular placing of granules with reference to the septa be recognised. Gomont himself, 

 however, queries this part of the diagnosis of L. layerhehni, and his figures certainly 

 fail to show anything of the kind. The cells of the trichomes were generally slightly 

 longer than broad (fig. 78). The apex of the trichome appears to be rounded and 

 obtuse. 



Genus PHORMIDIUM Kiitz. 



37. PHORMIDIUM AUTUMNALE. 



(PI. L, figs. 53, 54.) 

 Phormidium autumnale (Ag.) Gom., torn, cit., pp. 187-190, PL V., figs. 23, 24. 



Diam. trich. = 3 8-4 ' 5 p; long. cell. = 3 8 p. 



Ilab. Freshwater pond, Granite Harbour, January 20th, 1902. 



The cells were sometimes a trifle longer than broad ; the septa were marked by 

 a prominent double row of granules. The apex of the filament was not always 

 prominently attenuated (fig. 53), but was markedly capitate, the apical cell being 

 depressed-conical. 



This species was not as abundant in my material as in that examined by 

 Messrs. West (cf. op. cit., p. 291) ; in the locality above named it, however, evidently 

 formed extensive pure strata. 



38. PHORMIDIUM LAMINOSUM. 



Phormidium laminosum Gomont, Essai de classif. d. Nostoc. homocystees, Journ. de Bot., iv. (1800), p. 355 ; 

 Monogr. Oscill., torn, cit., pp. 167-168, PL IV., figs. 21, 22. 



Diam. trich. = 1-1 *5 /u, ; cellulis saepe elongatis (usque ad 5 p,). 



Hob. Gap pond, Winter Harbour. 



The cells were frequently much elongated, but apart from that the specimens 

 agreed well with Gomont's description. The inconspicuous septa were generally 

 provided only with two granules, one on either side ; according to Gomont there are 

 four, but his figures fail to show more than two. The bulk of Phormidium from the 

 Gap pond appears to belong to this species. 



