sheath. The shaggy-coated, rope-like stem is then often a line or more iu 

 diameter ; the major branches ^-| line, and the lesser ones proportionately 

 less thick, as the coat of fibrils is less developed. The ultimate branches 

 generally remain nude ; they are remarkably straight and rod-like, about 

 2 inclies long, and bear at every node, in alternate but laxly spiral order, 

 short flabelliform ramuli. The ramuli are 1-2 lines long, several times 

 forked, their segments of equal length. The articulations of the branches 

 are 5-8, of the ramuli 4-5 times as long as broad ; the cell-walls are thick 

 and gelatinous, and the endochrome narrow. Tetraspores are borne in the 

 forks of tlie ramuli, on very short pedicels. The colou7- is a clear pinky-red, 

 rapidly discharged in fresh-water. The substance is soft ; and the plant very 

 quickly decomposes in the air or in fresh-water ; and in drying adheres very 

 strongly to paper. 



The genus Callithmnnion is a very large one, dispersed through 

 almost all seas, having many representatives in Australia, and 

 comprising several more or less distinctly marked subtypes or 

 subgenera. Notwithstanding the wide differences of habit, and 

 of degree of development between the several species, I prefer 

 keeping the genus nearly as left to us by Lyngbye, and as re- 

 tained by J. Agardh, to breaking it up into several. The species 

 now figured is obviously allied to the European C. corpnbosum, 

 and to the Australian C. flabelUgerwn, C. ^riffithsioides, etc., 

 but by the characters of its stem it would fall under the " Sjoon- 

 godonium " of Sonder ; a genus proposed to be founded on my 

 Call, tingens (Alg. Exsic. Austr. n. 508), and to which several 

 other Austrahan species may be referred. All these agree in 

 having their stems and larger branches at least, coated externally 

 with a spongy mass of interwoven filaments, increasing with the 

 age of the specimens, and obviously of the same nature as the 

 internal filaments that in other species cause opaque stems and 

 branches, and define Kiitzing's genus PJdebothamnion. There 

 is this objection to employing as a generic character these sup- 

 plementary fibres, whether internal or external, namely, that they 

 vary in amount according to the age of the individual specimen. 

 Hence, a young frond may be referable to a gemis different from 

 that of its parent frond ; or, the branches of a specimen may 

 be " Callitliamnion' and the stem either " Phlebothamnion' or 

 " Spongoclonium!' 



Fig. 1. Callithamnion licmophouum, — the natural size. 2. A dichotornous 

 branchlet, and a single joint of a branch. 3. Tip of a branchlet, with axillary 

 tetraspores. 4. A tetraspore : — the latter figures variously magnified. 



