I here figure the commonest and therefore the most charac- 

 teristic of the Austrahan species of 8porocImiis, and also the 

 most variable. When growing in shallow water, as I have seen 

 it in King George's Sound, the substance is more rigid, the 

 diameter of stem and branches greater, and the ramification very 

 dense and stunted. In close proximity, but in deeper water, 

 the frond is slender, soft, and flaccid, and the branches drawn 

 out into long threads, two feet or more in length, and very 

 sparingly ramulose. Again, in the Tamar, Tasmania, the frond 

 attains still larger dimensions, and the branches are more at- 

 tenuated. Among hundreds of specimens examined, there is a 

 complete gradation in these respects. The form of the recepta- 

 cle and its proportion to the pedicel are also very variable in 

 this species. Our figure represents the average proportions 

 and shape ; but in some of the attenuated, deep-water speci- 

 mens, the length of receptacle is doubled ; in others it varies on 

 the same frond. 



Search should be made by Tasmanian collectors for the Sp. 

 Herculeus, J. Ag., formerly found by Mr. Gunn, at Georgetown, 

 and known by the very great length of its receptacles, — " six or 

 eight lines, or nearly an inch long, nearly entirely cylindrical, and 

 as thick as sparrow' s-quill." (See J. Ag. Sp. Alg. v. 1. p. 175.) 



Fig. 1. Sporochnus comosus, — the natural size. 2. Fragment, with the 

 receptacles, in situ, — magnified. 3. Some of the sporiferous filaments of the re- 

 ceptacle, — highly magnified. 



