SEPTEMBBa 3, 1909] 



SCIENCE 



309 



extremely erratic in their behavior. It would 

 appear that the problem is not one of cultiva- 

 tion or fertilization and the cause and remedy 

 must be sought in an entirely different di- 

 rection. 



While it is a fact, well known to botan- 

 ists, that plants of the genus Diospyros are 

 dioecious (occasionally polymorphous or mon- 

 oecious), yet the question of sex as related to 

 the non-fruiting of the Japan persimmon, D. 

 Kahi, appears to have been entirely overlooked. 

 Examination, both macroscopical and micro- 

 scopical, of hundreds of flowers of different 

 varieties shows that the stamens in the pistil- 

 late flowers are abortive and no pollen is borne 

 in them. Without question, herein lies the 

 reason for Japan persimmons so often setting 

 no fruit, or only a very light crop — an abun- 

 dant supply of pollen at the proper time is 

 lacking and the only source of pollen for the 

 Japan persimmon is the chance supply fur- 

 nished by staminate trees of D. Virginiana. 

 So far as the records show, no male trees of 

 D. Eaki have been brought to this country. 

 A change in orchard practise is needed, and 

 as in the culture of Smyrna figs or dates, carob 

 bean and pistache nut, the planting of male 

 trees to supply pollen is a necessity, so in 

 orchards of Japan or other persimmons, the 

 presence of male persimmon trees, covering 

 the blooming period, is necessary to secure an 

 abundant setting of fruit. To this there are 

 doubtless exceptions, as some varieties (Tane- 

 Nashi, for instance) are almost invariably 

 seedless and apparently set and mature fruit 

 without being pollinated. Seedlessness is in 

 many cases due to environment and is not an 

 inherent character in fruits. It is often due 

 simply to lack of poUen. 



It is possible that some specimens of D. 

 Kaki in this country do produce pollen-bear- 

 ing flowers, but such trees are extremely rare, 

 and in ten years of observation, but one such 

 tree, a monoecious specimen of Tabers No. 23 

 has been noted. So infrequently do such 

 occur, it may not be too much to say that all 

 Japan persimmon seedlings originated in this 

 country have a strain of some other persim- 

 mon (usually D. Virginiana) in them. 



The problems connected with this matter are 

 being carefully investigated. 



H. Harold Hume 

 Glen Saint Mart, Florida, 

 May 10, 1909 



SCIENTIFIC BOOKS 

 The Else and Progress of the British Ex- 

 plosives Industry. Published under the 

 auspices of the Seventh International Con- 

 gress of Applied Chemistry by its Ex- 

 plosives Section. Small quarto ; pp. 418 ; 39 

 illustrations. New York, Whittaker and 

 Co. 1909. 



This is the first fruit of the congress held 

 in London, May 28 to June 2, 1909, which was 

 attended by some 3,000 members. This book 

 originated in a suggestion made to the Com- 

 mittee of the Explosives Section, which has 

 financed the project, on December 5, 1908, and 

 it is the product of the joint efforts of a large 

 number of collaborators, most of whom are 

 intimately connected with the special branches 

 of the industry of which they treat, under the 

 supervision of Mr. E. A. Brayley Hodgetts, 

 editor. The contents are classified into an 

 Historical Part, treating of gunpowder, nitro- 

 cellulose, nitroglycerine and its derivatives, 

 permitted explosives, percussion caps, Bick- 

 ford's safety fuse, fireworks, legislation, bib- 

 liography, chronology and list of gunpowder 

 makers; and a Descriptive Part, treating of 

 the three existing government establishments 

 and some fifty-four private establishments. 

 The bibliography and chronology fill some 

 132 pages, while there are, in addition, con- 

 siderable lists of papers and patents attached 

 to some of the special articles, and these are 

 quite useful, but the special articles, as might 

 be expected from so large a number of con- 

 tributors, and especially where so many of 

 them are engaged in other than literary or 

 scientific pursuits, exhibit a marked uneven- 

 ness in the method of treatment and the qual- 

 ity of the product. This lack of system is 

 especially to be noted in the part devoted to 

 private establishments where the accounts vary 

 from a two-line notice of one establishment to 

 a ten-page description of another. 

 In fact, a large part of the text could have 



