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On the Genus Isoetes. 



good fortune to possess, and possess exclusively in this little 

 island of Guernsey, the only British representative of the terres- 

 trial section ; and this is the more interesting as the genus is 

 normally aquatic ; in fact Berkeley in his " Crypto gamic 

 Botany " observes in speaking of Isoetes "All the species are 

 strictly aquatic, and often grow in deep water, where they are 

 never uncovered in the driest season." 



The genus Isoetes seems to have been unknown to Eay, — 

 at least I find no mention of it in the 3rd Latin edition of his 

 " Synopsis Stirpium Britannicarum " published in 1724. — Lin- 

 naeus, in his " Sy sterna Naturae " 13th edition, 1788, gives the 

 generic character of Isoetes and describes two species, J. 

 lacustris and I. coromandeliana, but without localities or 

 habitats. In Hooker's British Flora, 1st edition, 1830, we find 

 I. lacustris described, its habitat being " bottoms of lakes in the 

 north, Wales and Scotland," "a very singular aquatic" the 

 author observes ' 'its fructification being entirely concealed at 

 the base of the cellular subulate leaves." In the 5th edition 

 of the same work published in 1842 the same description is 

 used, but the following note is added :— " Mr. W. Wilson finds 

 two varieties in Wales, the one densely tufted with slender 

 erect leaves ; the other solitary with broader leaves widely 

 spreading." [The former is the true lacustris, and the latter 

 echinospora.'] In Mackay's 4 ' Flora Hibernica" published in 

 1836 is given, besides the description, a more detailed account 

 of the two supposed modes of fructification as observed by Mr. 

 Wilson. In Withering' s " Systematic arrangement of British 

 Plants," 6th edition, no mention is made of Isoetes at all, 

 although both the Lycopods and Equisetacese are described in 

 full. This intentional omission is very remarkable. Babing- 

 ton in his " Manual of Britsh Botany " describes J. lacustris 

 and I. echinospora as distinct species, whilst Hayward in his 

 "Botanists Pocket Book" regards them as varieties of each 

 other merely, but both these authors record /. hystrix as 

 occurring at Guernsey. 



