coasts, but only two of these, V. diclwtoma, Lynp^b., var. 

 marina, C. Ag., and V. thuretii, Woron., have been 

 definitely identified in the L.M.B.C. area. 



IV. Valoniace.e. 



The thallus in this order retains its primitive cellular 

 form or is branched, but shows no differentiation into axis 

 and appendages. The sporangia are formed directly from 

 portions of the vegetative thallus. 



One genus only occurs in the British Algal Flora, viz., 

 Halicijstis, included by Wille {loc. cit.) under Valonia. 

 H. ovalis was first discovered by Murray and Schmitz in 

 Loch Goil, in the Clyde Sea Area, in 1892, but later it was 

 found by Robertson at Lamlash, Arran (vide PInjcoIogical 

 Memoirs, Pt. II., and Journal of Bot., vol. XXXII., p. 

 345). 



V. CODIACE^. 



The Codiacese include 8 genera, viz. : CJiIorodesmis, 

 Fenicillus, Aurainvillea, BliipocephaUs, CalUpsygma, 

 Udotea, Halimeda, and Codium. The last named alone 

 occurs in English waters. 



The thallus of the Codiacese is of varied form and 

 organisation ; some genera, e.g., Halimeda, being inci-usted 

 with calcium carbonate. The filaments of whicli the 

 thallus is composed are profusely branched, and the 

 branches are closely interwoven and bound together in 

 such a manner as to form almost a definite tissue. 

 Generally speaking, the filaments so woven together 

 form a medullary region from which arise short swollen 

 branches, standing at right angles to the long axis of 

 the thallus, and forming a superficial limiting layer, 

 tlie so-calknl "palisade layer" or "tissue." l^'rom tlu' 

 sidos of these "palisade cells" arise the sporangia i>r 



