Since the L.M.B.C. Memoirs are primarily intended 

 for the nse of " students of Biology in oiir laljoratories 

 and in marine stations," or " woi-king privately at natural 

 history," it may be advisable to summarise briefly the 

 main features of the British marine Siphoneae, and more 

 especially the Codiacere, at the same time indicating the 

 general distribution of the species on our shores. 



The British representatives of the SiphonesB include 

 members of five different orders, viz. : Bryopsidaceae, 

 Derbesiaceae, Vaucheriaceae, Valoniacere, and Codiacere. 

 According to Holmes and Batters (A Revised List of the 

 British Marine Algse, Ann. of Botany, V., 1890) four of 

 these orders are represented in our flora by one genus 

 apiece- — in each case by the genus that gives the name to 

 the order. In regard to the fifth, the Valoniaceae, it may 

 be noted that the genus inhabiting British seas, viz., 

 Halicystis, had not been discovered at the date of the 

 publication of Holmes' and Batters' paper. 



I. Bryopsidaceae. 



The thallus in tin's order is freely branched in a pinnate 

 manner and ancliored to the sulistratum l)y rhizoids 

 which are extensions of the base of the chief axis. The 

 branching of the thallus may be bi- or tri-pinnate. Multi- 

 plication is effected by the conjugation of dissimilar 

 gametes. The female gametes are large and gi-een, the 

 male are small and brownish yellow. Both are provided 

 with two ciha. The actual fusion of the gametes has not 

 yet been observed. No other method of propagation is 

 known in the order. 



The Bryopsidaceae include only one genus, Brijopsis, 

 with about 25 species, chiefly inhabitants of warm seas. 

 Tn l^)i-itish seas two species occur, B. hypnoides, Lamx , an 

 inhabitant of the Englisli Channel, and IL plmnosa, C. Ag., 



