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island of Juan Fernandez, 420 miles oflf the coast 

 of Chili, the home for four years of Alexander 

 Selkirk (to whose adventures we owe Defoe's 

 creation of Robinson Crusoe), is interesting also 

 from a botanical point of view. The vegetation of 

 this oceanic island, 20 square miles in area with 

 basaltic cliffs rising to a height of 3000 ft. above 

 the sea, includes more than 40 species of ferns, 

 eight of which occur nowhere else. One of these 

 endemic ferns is Thyrso2:tteris elegans, the only 

 representative of the genus ; it is readily distinguished 

 by its large and graceful fertile fronds, examples of 

 which may occasionally be seen on a plant of this 

 species in the Royal Gardens at Kew : the sporangia 

 are produced in circular cups which replace the 

 ordinary leaflets on the lower branches of the frond 

 and hang from the short axis like miniature clusters 

 of grapes. It is noteworthy that among the frag- 

 mentary remains of the fern vegetation of the Jurassic 

 flora in England and in other parts of Europe 

 specimens occur with fertile segments practically 

 identical with those of the Juan Fernandez species. 

 Students of fossil plants are occasionally led away 

 by the temptation to identify imperfect specimens 

 with rare existing species to which they exhibit a 

 superficial resemblance, and this is well illustrated 

 by tlie frequent use of the generic name Thyrsopteris 

 for Jurassic and Lower Cretaceous ferns which are 



