201 



of tlu'se puz/lini; plants, that thc\' have used to spleiKhd ad- 

 vantage. 



Detailed cominent of such a large work is obviously impossible, 

 but mention should be made of the scheme the authors have 

 followed. There are, of course, keys to the tribes, genera under 

 the tribes, and to the series and species where the genera are 

 large enough to need such subdivisions. 



For each of the species there is a complete synonymy, and 

 where, as in Opmitia, there are 900 names known for about 250 

 plants this will be of great value. There follows a description of 

 the species, a statement of its type locality and the distribution 

 of it. Notes of its variants, its affinities to related species, 

 illustration of it and other items, complete the record of the 

 treatment. Very nearly all the species are illustrated by photo- 

 graphs of mature plants, drawings of significant parts, or by 

 colored illustrations of the joints or filowers or fruits. No recent 

 botanical work has such a wealth of illustrations, and in such 

 plants as the cactus, which exhibit different characters at different 

 periods of growth, these are of paramount value in aiding iden- 

 tification. 



The prickly pears, comprising four fifths of the volume, are 

 grouped into 3 subgenera and 46 series, the characters of which 

 are based on a study of living plants of which the New York 

 Botanical Garden and the Department of Agriculture now ha\e 

 the largest collections known. Scores of cases of mistaken 

 identity, of the description of stages of one species as several, of 

 mistaken ideas of distribution and the other hazards due to the 

 difificulty of the group and early misconceptions, are now straight- 

 ened out. The gardener, field botanist, plant geographer and 

 ecologist can now find for the first time an accurate record of the 

 species and their distribution. Such a work and its changes 

 will produce shocks to the mentally well-intrenched, as for in- 

 stance, that the supposedly widely distributed Opuntia tuna is 

 actually confined to the lowlands of Jamaica; that 0. vulgaris 

 Mill, long supposed to be native here-abouts, does not occur in 

 North American except as an escape in Cuba, and many other 

 errors that have passed current. 



