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Contents of 1 Hooker's Journal of Botany ,' No. 19, July, 1850. 



Continuation of Mr. Spruce's Letters from South America. 



Report on the Dried Plants collected by Mr. Spruce in the neigh- 

 bourhood of Para. By George Bentham, Esq. 



Continuation of Dr. J. D. Hooker's Letters from India. 



Botanical Information : Victoria Regia. 



Notices of Books : Martius's Genera et Species Palmarum. The 

 Gardener's Magazine of Botany, &c. 



Botanical Society of London. 



Friday, July 5, 1850. J. H. Wilson, Esq., F.L.S., in the chair. 



J. P. Norman, Esq., of London, and T. Dutton, Esq., of Bath, 

 were elected members. 



Mr. George Maw exhibited specimens of Lilium pyrenaicum, dis- 

 covered by him between South Molton and Mollond, Devonshire, in 

 June last. 



Dr. Arthur Hassell read a paper " On the Colouration of the Water 

 of the Serpentine." In this communication it was shown that the 

 periodical and vivid green colouration of the water of the Serpentine is 

 due to the presence of a minute plant belonging to the tribe of Algae, 

 of which the writer gave a detailed and critical description, and which 

 he named Corriophytum Thompsoni. The development of this plant 

 takes place early in the spring, out of sight and at the bottom of the 

 water, and it is only on the approach of the warm weather of summer 

 that it diffuses itself through the water, deeply colouring it, and that 

 part of it rises to the surface, forming a scum or pellicle of a bright 

 aeruginous or coppery-green colour. The whole of the water of the 

 Serpentine is not usually coloured at one time, but different portions 

 of it at different times, according to the strength and direction of the 

 wind which drives the plant before it ; at one time it is found col- 

 lected at the Hyde Park extremity, at another it is present in the 

 Kensington division, sometimes on the north, and at others on the 

 south shore, the remaining parts of the Serpentine being entirely free 

 from the plant. This variable distribution, which, unexplained, 

 would be apt to occasion surprise, accounts for the fact that the ob- 

 server may sometimes visit the Serpentine and not see a trace of the 



