RHODOMELACE^. 93 



branched at intervals ; the branches three or four times 

 pinnated, beset with spreading or renexed branchlets, which 

 are about half an inch long, aud much more slender than 

 the main stems. The tips of both the branches and branch- 

 lets are strongly incurved. Neither spores nor tetraspores 

 are usually found on British specimens. 



This species is the only representative of the genus 

 in our flora, — I was going to write marine flora, but 

 that would not have been strictly correct, for it is com- 

 monly found among the roots' of flowering plants at the 

 estuaries of rivers, and in salt ditches and marshes. 



Genus XL. RYTIPHLCEA. 



Frond cylindrical or flattened, shrub-like, striped cross- 

 wise, composed of a jointed axis of large tubular, elongated 

 cells of equal length, surrounded by a periphery of one or 

 more series of irregularly-shaped, small, coloured cells. 

 .Spores pear-shaped, arranged in tufts in ovate concep- 

 tacles with or without stalks; tetraspores in terminal, 

 spindle-shaped branchlets, or in single or double rows, in 

 stichidia. — Rytiphlcea, from the Greek rutis, a wrinkle, 

 and phloios, bark. 



The characters of this genus are very similar to those 

 of some species of Polysiphonia, the most easily defined 

 difference between the two genera being, that in Ry- 

 tiphlcea the frond is composed of nearly equal parts of 

 axis and periphery, and consequently the joints of the 

 former appear at the surface only as stripes, while in 

 Polysiphonia nearly the whole bulk of the frond consists 

 of jointed tubes, similar to those in the axis of Ryti- 

 phlosa ; and either there is no periphery, or it is a mere 

 bark, and the articulated structure of the plant is, there- 



