178 NOTES ON AUSTRALIAN MARINE ALG.E, ii., 



brevioribus, content u tenuigranuloso farctis, dissepimentis non 

 aut vix granulatis. 



An Oscillatorian consisting of bundles of trie-homes, apparently 

 the shortest in the genus, not more than 0*5 mm. long. Colour 

 when preserved in formalin dusky brown. Trichomes straight, 

 not constricted at the genicula, nor attenuated toward the apex, 

 '.) or 10/x thick, the articuli one-third the width of the trichome, 

 with a finely granular content. Apices rounded, hemispherical, 

 without calyptra. Dissepiments nearly or quite clear. 



Samples of this alga were forwarded to me by Mr. A. R. 

 McCulloch, of the Australian Museum. I append his notes: — 

 "An alga which 1 collected at Hope [slands, near Cooktown, in 

 •June, 1918. It covered the sea like sawdust everywhere, and 

 formed long streaks or waves across the wind. It was so abund- 

 ant as to cause smooth patches unbroken by wavelets where it 

 occurred, and was of a light brown colour, the tint apparently 

 varying according to its stage of development. On the Hope 

 Islands it had blown up on the wave-line, and formed felt-like 

 flakes which could be picked up in pieces a foot square and 3-5 

 mm. thick; the flakes were very dark in colour, and stained the 

 sand-grains settling on them a rich violet. The alga is very 

 buoyant, and causes a muddy appearance in the water as the 

 boat disturbs it. An old hand up that way assured me that its 

 presence was a sign of good weather, and it certainly seems to 

 disappear at the approach of wind and clouds. 



I believe this alga was seen by Cook, whose sailors named the 

 region the Sea of Saw-dust on account of its presence. It is of 

 very great importance as a food item to a large number of the 

 reef animals." 



The genus Trichodesmiwm, as De Toni writes "A gen. Oscilhi- 

 toria vix distinguendum," is a convenient subgenus at all events, 

 for the inclusion of those Oscillatorire which are met with in 

 immense societies floating on the surface of chiefly the equatorial 

 seas They include the species T. eryihrceum Ehr., which gives 

 the red colour, and hence the name, to the Red Sea. in the 

 generic characters a calyptra is included, There is no calyptra 



