292 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



''Introduction to Science." By Prof. J. A. Thomson. 



" Evolution." By Prof. J. A. Thomson and Prof. P. Geddes. 

 Each 32mo., 256 pp. (Wilhams & Norgate, London, 1911.) Is. 

 net each. 



These are eminently readable essays forming two volumes of the 

 "Home University Library of Modem Knowledge." The general 

 editor, Prof. J. A. Thomson, is a well-known writer on evolution and 

 kindred subjects, and is known as well for his lucid exposition and 

 scholarly English as for his wide knowledge and deep understand- 

 ing. They are books which everyone, no matter what his line of 

 thought may be, might read with profit and no little pleasure. 



" Cacao: A Manual on the Cultivation and Curing of Cacao." By 

 J. Hinchley Hart, F.L.S., late Superintendent of the Eoyal Botanic 

 Gardens, Trinidad. 8vo., 307 pp., with numerous illustrations. 

 (Duckworth, London, 1911.) 7s. 6d. net. 



The late Superintendent of the Trinidad Eoyal Botanic Gardens 

 was an authority on the subject of cacao cultivation and curing, and 

 it is with much regret that v^e find it necessary to state that he was 

 removed by death before his valuable book issued from the press. 

 Having a practical knowledge of every detail connected with cacao, 

 from the selection of suitable land for a plantation to the curing of the 

 " beans " for export, and also an acquaintance with the trees in their 

 native habitat. Hart was eminently qualified for the task he undertook, 

 and in discharging it he has acquitted himself well. 



The book opens with a discussion of the botany and nomenclature 

 of the species of Theobroma, to which genus the cacao-tree belongs. 

 Some nine species are Known tO' botanists, but of these only Theohroma 

 Cacao and T. pentagona appear to be of commercial importance. To 

 the Mexicans Theobroma Cacao is known by the name of " Cacao- 

 quahuitl," which to a large extent is retained in the word " chocolate." 



The selection of land for a cacao plantation is an important matter, 

 and the subject is dealt with in this book in a practical manner. 

 Hitherto cacao-trees have been invariably propagated by seed, and as a 

 consequence scarcely two plantations or even two trees produce 

 " beans " of the same kind. To remedy this the author advocates a 

 system of grafting whereby desirable kinds may be increased to any 

 extent and the type fixed. The " approach " system of grafting has 

 proved successful, and this method of propagation will probably gain 

 favour in tHe future, and a more uniform kind of " bean " will be 

 marketed. 



In discussing the vexed question of shade for cacao the author con- 

 fesses to a change in opinion on the subject, and admits the necessity 

 of shade for cacao-trees, which he considers should be sufficient but 

 neither too dense nor too light. With regard to manuring, the mulch- 

 system is recommended owing to the surface-rooting habit of the tree, 

 but the author is careful to point out that only trees in poor soil or 



