Dr. Dickie on the Marine Algce of the vicinity of Aberdeen. 331 



short free brandies, about half an inch in length ; margins of 

 apertures with a deep notch, which is filled up by a transparent 

 membrane. 



3. P . fruticosa , nov. spec. — Polypidom shrubby, adherent in 

 but a small part of its extent, suddenly dilated towards the aper- 

 tures ; margins of apertures entire. 



Genus Fredericella. 

 Char. — Polypidom fixed, coriaceous, tubular, branched. Po- 

 lypes issuing from the extremities of the branches ; tentacular 

 disc orbicular ; tentacula arranged on the margin of the disc in a 

 single series, less numerous than in Plumatella (about twenty- 

 four), invested at their origin by a membrane. 



1. F. Sultana. 



2. F. dilatata, nov. spec. — Polypidom dilated towards the aper- 

 tures. 



Family PALUDICELLAID^. 

 Genus Paludicella. 

 Char. — Poljqjidom fixed, coriaceous, consisting of a single se- 

 ries of claviform cells with a catenulated arrangement ; apertm-es 

 unilateral, tubular, placed near the wide end of the cell. Tenta- 

 cular disc of polypes orbicular, bearing upon its margin a single 

 series of tentacula ; tentacula free. 

 P. articulata. 



XL. — On the Marine Alga, of the vicinity of Aberdeen. By G. 

 Dickie, M.D., Lecturer on Botany in the University and 

 King's College of Aberdeen. 



[Continued from p. 10.] 

 [With a Plate.] 



Himanthalia lorea. — This remarkable plant is not uncommon at 

 Aberdeen. It usually occurs in detached patches : many parts of 

 the coast are destitute of it ; in other spots it is in great profusion, 

 and is most usually found near low-water mark. 1\\ this vicinity 

 it seldom attains any great size, rarely exceeding 2 to 2^ feet. 



Dr. Montague's statement, that it possesses both acrosperms 

 and basisperms on different individuals, is quite correct, as I have 

 verified by examining an extensive series of specimens. 



While the thong-shaped receptacles are still immature, their 

 surface is covered with numerous pores from which filaments 

 issue, and exactly resemble those on the species of Fucus, and 

 which in a former paper were stated to be barren conceptacles. 

 In Himanthalia they are generally all ultimately fertile, pro- 

 ducing, as already mentioned, either acrosperms or basisperms. 



