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IV. — On certain Phenomena observed in the genus Nitella, as illus- 

 trative of the peculiar structure recently discovered by Mr. 

 Bowerbank, in a Fossil Wood from the London Clay. By 

 Arthur Farre, M.D., F.R.S., &c. 



(Read November 25th, 1840). 



The observation of a new form of vascular tissue occurring in the 

 fossil wood from the London clay, as detailed by Mr. Bowerbank in 

 his paper read at the last meeting of the Society, has induced me to 

 offer a few remarks on an apparently analogous recent structure, which 

 I, several years ago, observed in some specimens of Nitella Jlexilis, 

 kept for the purpose of examining the circulation in that plant. 



Before proceeding to detail the result of my own observation, I may 

 be allowed to quote that portion of Mr. Bowerbank 1 s paper in which 

 this new fossil tissue is described. The author observes that in the 

 Heme Bay fossil " some of the vessels contain large vesicular globes, 

 which appear to have been freely floating within their parietes ; when 

 not in contact with each other they are perfectly globular and un- 

 compressed." " They vary very considerably in size, in some cases 

 filling nearly the whole diameter of the vessel, while in others they do 

 not occupy a tenth of that space. They are frequently so numerous 

 that they fill the whole of the vessel. The structure of which these 

 globular bodies is formed is thin and very pellucid, and no fibre or 

 other organic structure is apparent upon its surface. There are also 

 in some of the vessels, exceedingly small vesicles interspersed among 

 the larger ones. A portion of these are opaque and black, but the 

 greater number of them are transparent like the larger ones. These 

 very minute vesicles do not exceed in size the globules of circulation 

 in Vallisneria ; and as we find vesicles of every size intermediate be- 

 tween these minute ones and the largest of the vesicles, it appears 

 probable that the whole of them may be attributed to a more than or- 

 dinary development of globules of circulation, analogous to those ob- 

 served in Vallisneria and other plants." The author further remarks 

 that he has " never seen this curious form of tissue in any other wood, 

 either recent or fossil ; though he had " occasionally observed very 

 similar large pellucid globules slowly moving in the great central ca- 

 vity of the stem (of Chara), while the circulation of the smaller glo- 

 bules in its parietes has been proceeding with a much greater degree 

 of rapidity." 



These particulars, with reference to the structure of the fossil wood, 



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