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XI. Observations on the natural Group qf Plants called Pom ac e;e. 

 By Mr. John LinHjey, F.L.S. 



Read April 4 and 18, 1820. 



The natural group of plants comprehended in the first section 

 of Jussieu's Rosacece has, on account of its near affinity to Rosa, 

 lately occupied much of my attention ; and as an apparent uni- 

 formity in the structure of its genera has been the cause of much 

 dispute respecting their limits, an attempt to ascertain these with 

 something like precision may not perhaps be unacceptable to 

 the Society. 



Linnaeus admitted but four genera, Crataegus, Sorbus, Mespi- 

 lus, and Pyrus ; from which Jussieu distinguishes Malus and Cy- 

 donia. Medicus, in his " Geschichte der Botanik nnserer zeiten," 

 published in 1793, out of these formed eleven, in which he has 

 been partially followed by Borkhausen and Monch. His genera 

 are unfortunately by no means natural ; and the characters upon 

 which they are founded have been considered unimportant by 

 most botanists, who have therefore adopted the genera of either 

 Jussieu or Linnaeus. Sir James Smith, aware of the uncertainty 

 in number of styles by which those of the latter have been prin- 

 cipally distinguished, has in Flora Britannica and Rees's Cyclo- 

 pedia (article Mespilus) reduced all the genera to two ; charac- 

 terizing Pyrus, to which he refers Cydonia and Sorbus, by the 

 thin texture of its endocarp, and Mespilus, including Cratcegus, 

 by the osseous substance of the same part, or, as he, following 



Linnaeus, expresses it, by its berry. 



But 



