248 SEAWEEDS 



pollinoid pass into and unite with those of the female 

 cell. There is no development of gonimoblast, but 

 the whole of this fertilised cell becomes a spore and 

 emerges from its membrane, or it first divides once or 

 twice and forms several spores. The whole of this pro- 

 cess may represent a very much reduced or an ancestral 

 Rhodophycean type, but there is a great gulf between 

 it and the simplest form of indubitable Red Seaweed. 

 The non-sexual spores, the so-called tetraspores, of 

 Bangiacece leave us also in doubt. The whole of the 

 contents of a single thallus cell go to the formation 

 of one of the spores which are unciliated, at first 

 without a membrane, but afterwards with one. In 

 some cases there is a preliminary division (once or 

 twice) of the thallus cell. It may be recalled that 

 monospores (the undivided tetrasporangium) occur 

 in certain Rhodophycecc, but even then there is no 

 conclusive evidence here for or against, though it 

 leans towards inclusion. On the whole, and con- 

 sidering the difficulty of placing them elsewhere, the 

 Bangiacece may be left beside the Rhodcphycea, though 

 not within the group. 



The Geographical Distribution is world wide. It is 

 however a small order with comparatively few species, 

 though these are of very variable character. Bangia, 

 Goniot-richum, Erythrotrichia, Parphyra, and Diplo- 

 derma, are all British, and most of them abundant on 

 our shores. The species of Porphym furnish the 

 edible Laver. 



