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On the Anomalous Structure of the Leaf of Rosa berberifolia. 

 By Mr David Don, Librarian to the Linnean Society, 

 Member of the Imperial Academy Naturae Curiosorum, 

 of the Royal Botanical Society of Ratisbon, and of the 

 Wernerian Society of Edinburgh, 8ic. (Communicated by 

 the Author.) 



.1 HE ordinary leaf of Rosa is compound, being generally com- 

 posed of an indefinite number of pairs of leaflets, terminating 

 with an odd one :, and the lowest pair, although present in the 

 form of stipulae, are considerably modified, being found to be 

 more or less confluent with the general petiolus. This view of 

 the origin of the stipulae, in this genus, is clearly shewn by the 

 ultimate leaves, or bracteae, in which the various degrees of mo- 

 dification may be observed. The stipulae of Rosa vary much 

 in size ; in some species they are large and foliaceous ; in others, 

 such as Rosa Banksice, microcarpa, and sinica, they are small, 

 and so very fugaceous as to be only observed in the early stage 

 of the leaf. As in other extensive genera having compound 

 leaves, it might be expected that Rosa would also contain spe- 

 cies, in which a reduction in the number of leaflets takes place. 

 In Rosa sinica and hystrix the leaflets are only three ; while in 

 Rosa berberifolia, and in a second species, known only from a 

 representation contained in a collection of Chinese drawings pre- 

 serv'ed in the library at the India House, the leaf is reduced to 

 its simplest form. The compound nature of a leaf reduced to 

 its simplest form is always indicated by the presence of an arti- 

 culation. A casual inspection of the leaves of Rosa berberifolia 

 would lead one to conclude that the stipulae were entirely want- 

 ing ; but a more attentive examination shews that these organs 

 are also present in this plant, although under a very anomalous 

 form. Immediately under the leaf we find a callosity forming 

 a prominent ridge on the branch, attenuated towards the base, 

 and terminated by two or three spines. This callosity evidently 

 originates in the confluence of the stipulas with the stem. The 

 leaf itself, surrounded by the spines, is situated immediately on 

 the summit of this callosity, to which it is articulated by its very 

 short footstalk. The articulation is particularly distinct, and 



