of the vicinity of Aberdeen. 109 



after a gale, and a few days subsequently I found some very large 

 examples near the mouth of the Dee. 



D. aculeata, Lamour. — Is very abundant, and, like the former, 

 an inhabitant mostly of deep water ; on one occasion only have I 

 seen it in situ at low-water mark. 



Owing to the localities in which these species grow, no oppor- 

 tunity has been afforded of procuring them at different seasons 

 in states favourable for microscopic examination. The fructifica- 

 tion has by some been supposed to be connected with the pencils 

 of filaments which are plentifully produced. The structure of 

 these filaments differs essentially from that of the simple or 

 branched filaments which usually accompany the spores and spo- 

 ridia in other Algae ; in Desmarestia they are generally flattened, 

 being composed of several slices of cells on the same plane, and 

 often appear like fronds in miniature. It is by no means impro- 

 bable that they afford one way by which the plants are propa- 

 gated. The very fact that these filaments (miniature fronds ?) are 

 so copiously produced, may be the very reason that neither true 

 spores nor sporidia have hitherto been found. Among Phseno- 

 gamous plants there are examples of what may be an analogous 

 mode of reproduction, as in Saxifraga foliolosa, Br., of the Arctic 

 regions, and others; in mosses, as Macromitrium Leprieurii, Mon- 

 tagne. The same is no doubt true of some Lichens, and why 

 not also of Algse ? 



Mr. Lyell has presented me with specimens of D. aculeata 

 picked up on the beach of Cockburn Island, lat. 64° 12' S. : in 

 this desolate region the temperature may be unfavourable to the 

 development of true fructification, and the viviparous (?) mode 

 alluded to may be legitimately inferred. 



From the structure of the frond in our two species of Desma- 

 restia, I should be inclined to predict that the fructification, when 

 detected, will be found to consist of spores. 



Dictyote^e. 



Padina Pavonia, Lamour. — This beautiful plant is stated, in 

 Dr. GrevihVs 'Algse/ and in Sir W. J. Hooker's ' Flora/ to have 

 been found at Aberdeen. The statement, I believe, was first 

 made by Lightfoot, on the authority of Dr. Cargill ; I have often 

 searched for it, but in vain. 



Dictyosiphon fceniculaceus, Grev. — It occurs in pools between 

 high- and low-water mark, but nearer the former, in great profu- 

 sion and of large size. It may be reckoned among the most 

 common species. The fructification is stated, in ( Harvey's 

 Manual/ to be rare ; I have found it not unfrequently, but only 

 on distorted specimens, not exceeding three or four inches in 

 length. 



