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JOURNAL, R.A.S. (CEYLON). [VOL. II., PaKT II. 



Society, with a view of affording encouragement and co-operation 

 to native associations at outstations. After some discussion, in 

 which it was shown that new Rules could not be proposed except 

 at the Anniversary Meeting, it was resolved that the matter be 

 left for the consideration of the Committee. 



The following letter was then read from Mr. Thwaites of 

 Peradeniya, describing the nature of a vegetable substance received 

 by the Society from Mr. Edgar Layard of Point Pedro : — 



Royal Botanical Gardens, Peradeniya, 



June 13, 1850. 



My Dear Sir, — Directly I took into my hands the cotton-like 

 substance contained in your letter, and before I put it under the 

 microscope, I suspected it to be a species of Conferva (or fresh- 

 water Alga), and such it proves unquestionably to be. It is a 

 species of Tiresias of Bory (Vesiculifera, Hassall). 



In England it is no uncommon thing to find, after the subsidence 

 of floods, large quantities of what is called " vegetable flannel" 

 left upon fields which have been covered by the water ; and the 

 "vegetable flannel " I have always found to consist of one or more 

 species of Conferva matted together. The origin of this substance 

 has been a puzzle to many a naturalist, but is nevertheless easily 

 explained, and thus : — 



Previously to the fall of rain, every stagnant pool and ditch has 

 contained an abundance of these minute plants, which grow 

 floating without any attachment to the bottom or sides ; when 

 these pools, therefore, become overfilled, the Conferva are floated 

 out, carried away by the descending streams to the lower grounds, 

 and there left as the waters subside. 



The structure of these plants, as shown by the microscope, is 

 very simple : the whole plant consisting frequently of a single row 

 of similar cylindrical cells placed end to end : II ll ll || ~T 

 When in a growing state each cell has a small quantity of green 

 colouring matter, or " endochrome, " within it, differently arranged 

 in the different genera, and which almost disappears when the 

 plant is dead and dry ; and I should have been unable to identify 

 the genus to which the plant you have sent belongs but for 

 certain ring-like markings (a) upon the end of some of the cells, 

 and which are characteristic of the genus Tiresias in one of its 



a a a 



states of growth. ~1 II II 



I am, &c, 

 G. H. K. Thwaites. 



John Capper, Esq., 

 Secretary, Royal Asiatic Society. 



