108 Dr. G. Dickie on ike Marine Alga 



9. Unio striatus, Goldf. Petref. pi. 132. f. 3. 

 From coral rag, Nattheim. 



10. Unio liasinus, Zieten, Verst.Wurt. pi. 61. f. 2 ; Bronn, Lethaea 

 Geogn.pl. 19. f. 17. 



From Fildres near Stuttgard. This is evidently a Gresslya, 

 allied to Amphidesma rotundatum, Phillips. 



XV. — On the Marine Algce of the vicinity of Aberdeen. By G. 

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

 King's College of Aberdeen*. 



[Continued from vol. xiii. p. 335.] 

 [With a Plate.] 



Previous to entering on the remaining species of the olive- 

 coloured Algse found in this ncinity, it will be necessary to direct 

 attention to the difference usually understood between the repro- 

 ductive bodies called spores and sporidia. 



The remarks already made on the acrosperms {sporidia) of Fu- 

 cus, kc, and the accompanying figures, will sufficiently explain 

 their structure ; it must be observed, that up to the time of ma- 

 turity they are enclosed in cells {asci), from which, when ripe, 

 they are readily emitted. It is more than probable, however, 

 that there are instances in which there is an intimate adhesion 

 between the sporidia and their asci, so that both drop ofiF 

 together. 



The observations recorded in the first part of this communica- 

 tion, on the development of the seeds oiFucus serratus, will explain 

 the nature oospores ; the latter are not necessarily enclosed in cells 

 up to the time of maturity, but usually become free. 



A difference exists in many Algte between the appearance of 

 the contents of the spores and sporidia : in the latter, the granu- 

 lar matter has a tendency to cohere in masses, which often assume 

 a definite arrangement; the contents of the spores are more 

 abundant, so much so that these bodies are generally dark-co- 

 lom-ed and almost opake, — hence the expression Melanospermece, 

 and the granular matter probably never (?) assumes a definite 

 arrangement. 



SpOROCHNOIDEyE. 



Desmarestia ligulata, Lamour. — This species appears to be of 

 rare occurrence, strictly confined to deep water, and only found 

 cast up after storms. The first specimens were found by Dr. 

 Andrew Fleming in October last, on the beach near Don mouth, 



* Head bcibrc the Botanical Society of Edinbiu-gli, 11th .\\m\ 1S41. 



