108 SEAWEEDS 
form and division of one initial cell (or at most a 
small group) derived from the epidermal layer. 
The Reproductive Organs, both unilocular and pluri- 
locular, are either differentiated superficial or epi- 
dermal cells or outgrowths of these. They are 
accompanied or succeeded, as has been noted above, 
by the formation of paraphyses. While in such 
genera as Desmotrichum, Punctaria, &ec., the epi- 
dermal cells in question undergo but little differ- 
entiation, in Scytosiphon, Hydroclathrus, and other 
genera, the cells giving rise to plurilocular sporangia 
undergo considerable elongation and division in the 
process. The globular unilocular sporangia of Asper- 
vcoceus, standing free from the surface of the plant 
among paraphyses, originate in outgrowths from the 
epidermal layer—as the paraphyses do. 
The order is formed of three others recognised 
formerly as Punctariacee, Scytosiphonacee, and Asper- 
ococcaceee, together with the genera Cotlodesme and 
Myclophycus—a grouping of them justified by Kjcll- 
man (Engler and Prantl’s Nat. Pflanzenfamilien, 
part 1, p. 197). 
The Geographical Distribution is fairly even through- 
out all seas, but more abundant in temperate waters. 
Desmotrichum, Punctaria, Litosiphon, Scytosiphon, 
Phyllitis, and Asperococcus occur in British seas. 
RALFSIACEA, 
General Characters—This small order embraccs 
plants of a very undifferentiated vegetative structure 
and of a crust-like habit. The reproductive organs 
