NOTICES OF BOOKS AND MEMOIRS. 185 



plants of the family of MelastoniacefB, especially that of the genus 

 Acanthella, Hk. f., the flower of which he figures in a corner of his 

 plate. The pamphlet includes a description of the species of the 

 genus, which the author apparently considers should still rank as 

 a distinct family, comprising five species ; one of those species is 

 new, and is here described as such for the first time. The species 

 differ among themselves by the textm-e of the foliage, by the com- 

 parative density of the flowering cymes, by slight variations in the 

 shape of the calyx- tube, and by other small characters. 



It is evident that M. Decaisne's standard of a botanical species 

 is considerably lower than that held by many botanists of the 

 present day ; for of his five species, fom*, which are South African, 

 were described as varieties of one species in the second volume of 

 the "Flora Capensis " of Harvey and Bonder (1861-62), and even 

 the fifth species, which is Abyssinian, is. probably identical with 

 that which w^as described in the second volume of Oliver's " Flora 

 of Tropical Africa" (1871) as belonging to the aggregate species 

 of Sonder. M. Decaisne appears to have overlooked the last- 

 mentioned work, in which the geogi'aphical range of the species is 

 extended to Angola. 



In order to complete the synonymy of the genus, it may be 

 well to add that the genus Plectronia of Linnaeus, as originally 

 described by him in the year 1767, and as illustrated by the spe- 

 cimen which is still extant in his herbarium at the apartments 

 of the Linnean Society of London, excluding, however, the plate of 

 Burmau quoted by him, is identical with Thunberg's genus Olinia ; 

 and that Polysphceria / Ugustrifolia, Vatke, from Abyssinia, falsely 

 referred by its author to PiubiacecB, is a species of Olinia. 



The following key, extracted from M. Decaisne's characters, 

 may be useful for the discrimination of the species : — 

 Folia coriacea. 



Cymae densiflorae, terminales vel axillares. 



Tubus calycinus cylindratus, denticulatus . 1, 0. cymosa, Thunberg. 



Tubus calycinus apice subconstrictus, denticulatus. 



2. 0. capensis, Klotzsch. 



Tubus calycinus apice dilatatus, subinteger . 3. 0. acuminata, Klotzsch. 

 Cymse gracillimse, axillares. Calyx obconicus, integer. 



4. O. micrantha, Decaisne. 

 Folia submembranacea 5. 0. iiOc/?^fiawa, Adr. Juss. 



W. p. H. 



Bibliogrcqjhical Index to North American Botany ; or Citations of 



AutJiorities for all the recorded Indif/enous and Xaturalized 



Species of the Flora of North America. With a Chronological 



AiTangement of the Synonymy. By S. Watson. Part I. — 



Polypetaloi. (Smithsonian Miscellaneous Collections, 258). 



■ Washington, March, 1878. 



This is an admirable example of conscientious and well-directed 



labour, and indeed leaves nothing to be desired. Few books were 



more wanted by the systematic botanist than one which should 



collect together the extensive and fragmentary literature bearing 



