CBTPTONEMl L( 1-7 



ady places, among Zostera, near low -water mark. 

 Annual. Summer. 

 The structure of this speciea differs considerably 

 that of the preceding, and probably may justify the future 

 formation or a genus, r hen the fructification or both plants 

 shall be more perfectly know n. In our -V. pwrpurt urn, the 

 axis is composed of much more Laxly set filaments ; while 

 those of the periphery are less branched, shorter, and com- 

 posed of very large, pear-shaped cells. Seen under a Lens 

 of Low i><»\vcr, thf branches appear Like tubes of glass, 

 densely covered with brilliant purple Btuds. -V. purpu- 



is a rare species on the British shores, though 

 sionally thrown up in considerable quantities. 



LWVITT. DUDBESNAIA. 



220. coccinea (The scarlet Dvdresnaia) j frond rosy-red, tender 

 and gelatinous, much and irregularly branched ; branches 

 alternate, ilcxuous, monililorm, attenuated upwards ; raniuli 

 more or Less numerous, Bonnem. in Journ. Phys. c. <JJ, p, 

 lso. (Atlas, PL WAX. Fig. 220.) 



Mesogloia coccinea, Ag. Rivularia verticillata, E. Bot. 

 J I <ib. On rocks, etc. near Low-water mark ; or, more generally, in 

 I fathoms water. Annual. Summer. Very rare. 

 Ouo of the rarest of the British Algae, scarcely known 

 except on the southern shores ^( England, and there only 

 in a feu stations, and nowhere in great abundance. Per- 

 haps one cause of its comparative rarity is its place of 

 growth. Being a deep-water species it is rarely found ex- 

 cept when casl a>hoiv after a gale, or when BOUght by 

 dredging. In the former case the specimens are frequently 

 very flaccid, and faded in colour. There is considerable 

 difference in structure and also in appearance between 

 young and old plants. In the former the axis i- a simple, 

 jointed filament, nol \ery unlike thai of a G-riffithsia s 

 whorled at Bhorl intervals with headed fibres. But as the 

 plant increases in aL, r c the axis becomes more compound, 

 until it consists kA' a bundle of closely packed filaments; 

 and then the branches become thicker and more cylindrical, 

 ommonly produced in abundance. Tetra* 



- are much more rare. 



221. divaricata {The divaricate Dudresnaia)] frond filiform, 

 pale-red, very much branched; branches opposite or alter- 



n iee pinnated ; raniuli num 



