110 Dr. G. Dickie on the Marine Alga 



Punctaria plantaginea, Grev. — Is not uncommon in summer 

 in pools near high-water mark. 



Asperococcus echinatus, Grev. — Not uncommon along with the 

 former. 



A. pusillus, Hook. — A plant corresponding to the description 

 usually given, and resembling in structure authentic specimens 

 sent me by Mr. Thompson of Belfast, occurs here, though rarely ; 

 it is usually parasitical on Polysiphonia nigrescens, but very small. 



Chorda lomentaria, Grev. — Not unfrequent in pools near high- 

 water mark. 



C.filum, Lamour. — This species, so common on many parts of 

 the British coast, and attaining so great a size as that mentioned 

 in the 'Alga? Britannicae/ is comparatively a rare plant in this 

 vicinity, occurring only in deep pools at high-water mark, and 

 seldom exceeding two feet in length. I have seen it in the small 

 harbour of Stonehaven attached to stones imbedded in mud, and 

 attaining a greater size than at Aberdeen. Dr. Greville describes 

 the fructification as consisting of " external masses of pear-shaped 

 seeds fixed by their base," and gives a figure of these ; he how- 

 ever alludes to a second kind, composed of " sessile ovate cap- 

 sales scattered among clavate articulated filaments," discovered 

 by Captain Carmichael and figured in ' Flora Londinensis/ The 

 bodies described and figured in the ' Algae Britannicse' constitute 

 merely the cortical tissue of the plant ; the true fruit, consisting 

 of asci and sporidia, is imbedded in that tissue, and probably 

 identical with the bodies seen by Carmichael and represented in 

 the l Flora Londinensis/ which I have no opportunity of con- 

 sulting. I consider it unnecessary to give any representation of 

 this true fructification, since it exactly resembles that of Alaria 

 and Laminaria already figured. 



Ectocarpe^e. 



Cladostephus verticillatus, Lyngb., and C. spongiosus, Ag., are 

 both not uncommon in pools within high-water mark. 



Sphacelaria plumosa, Lyngb. — Is one of the rarest of our olive- 

 coloured Algae ; only a few small plants, not exceeding an inch 

 in height, have been found in pools within high-water mark. 



S. cirrhosa, Ag. — At least two of the varieties of this species 

 occur abundantly in pools. 



S. olivacea, Ag. — Appears to be rather local ; it occurs on per- 

 pendicular faces of rocks near low-water mark. 



Ectocarpus littoralis, Lyngb. — Is very common on the coast, 

 and found abundantly about the mouths of the Dee and Don ; it 

 passes more than a mile up the former river, and often grows 

 luxuriantly in places where at low-tide it is freely exposed to a 

 strong current of fresh water. 



