334 



NA TURE 



[January 20, 19 10 



belief that the power to affect the protoplasm so as to 

 lead it to produce structures useful to the gall-makers 

 has been acquired independently by numerous organ- 

 isms (plants as well as animals), in widely different 

 grades of development. If that is so, it seems reason- 

 able to expect that power to control the activity of 

 protoplasm will, at least to some extent, be acquired 

 by man, and may produce results of great value. Al- 

 though as yet experiments have thrown little light on 

 the artificial production of galls, there is a very 

 attractive field open for research in this direction. 



Since 1870 an extensive literature has appeared deal- 

 ing with galls, dispersed so widely that much of it was 

 almost beyond reach of even keen students in this field. 

 In 1858 G. von Haimhoffen estimated the known galls 

 of Europe at from 300 to 350. In Kaltenbach's 

 " Planzenfeinde," issued in 1873 and 1874, the galls 

 of Central Europe formed by insects, and by a few 

 mites, were described under the host-plants ; and from 

 1890 to 1895 D. von Schlechtendal issued a catalogue 

 of the galls of animal-origin then known to occur in 

 Germany. 



In 1901 appeared two works giving brief descriptions 

 of the galls of Europe and of the Mediterranean area, 

 Kieffer's "Synopsis des Zooc^cidies d'Europe," and 

 Darboux and Houard's "Catalogue systematique des 

 ■Zooc6cidies de I'Europe et du Bassin M^diterraneen." 

 These were most welcome, and stimulated research so 

 greatly that a new catalogue had already become neces- 

 sary when M. Houard supplied the need by his latest 

 work, "Les Zooc^cidies des Plantes d'Europe et du 

 Bassin de la M^diterran^e." Based upon the "Cata- 

 logue," and covering the same area, comparison of 

 the two shows remarkable progress during the few 

 years that elapsed between their dates of issue. Such 

 a comparison is a little hindered by the' host-plants 

 being arranged in the earlier list in alphabetical order 

 of the generic and specific names, while in the later 

 they are in families, these following the order in 

 Engler's " Pflanzenfamilien," while within each family 

 the genera and species are grouped after Nyman's 

 "Conspectus Florae EuropeEe." The advantages de- 

 rived from the re-arrangement of the host plants be- 

 side their allies far outweigh those of the alphabetical 

 arrangement. 



The comparison between the individual hosts in 

 the two lists shows very careful revision of the descrip- 

 tions common to both, the omission from the second 

 of some forms included in the first, the definite refer- 

 ence to their makers of numerous galls previously of 

 unknown or doubtful origin, and the addition of many 

 recently discovered galls, some on plants already 

 known to bear galls, others on new hosts. A rough 

 indication of the advance is given in the rise of the 

 marginal numbers attached to the galls from 4169 to 

 6239 ; but perhaps a truer value is afforded by the in- 

 crease of the host-plants in much the same proportion, 

 and of the known gall-makers from 1072 to 1366 

 species, the increase being especially large among the 

 Curculionidae (beetles), the Cynipidce (gall-flies), the 

 CecidomyidcE (gall-midges), and Eriophyidse (gall- 

 mites). Numerous additions have been made to the 

 very useful illustrations scattered through the book. 

 NO. 2099, VOL. 82] 



An important addition is a bibliography of the Uter- 

 ature on galls, which, though not complete, is the best 

 that has vet been published, and will be found most 

 helpful as a guide, while its value is increased by refer- 

 ences to it under each gall ; and the countries in which 

 the galls have been found are also indicated very 

 briefly, yet simply. Under each host-plant the galls 

 are arranged on the same method as was employed in 

 the "Catalogue systematique," viz., terminal galls of 

 fruits, flowers, stems, and buds, followed by lateral 

 growths on roots, stems, branches, leaves, &c. In 

 most cases this method makes it possible to ascertain 

 the name of any gall without serious difficulty ; but 

 on some of the oaks and a few, other plants the forms 

 are so numerous as to lead to further subdivision of 

 the groups by subordinate characters. 



The arrangement of the plants in families has 

 allowed a brief but suggestive outline of the leading 

 features of the galls characteristic of each family, and 

 of occasional suggestions for inquiries. 



Careful indexes of the host-plants and of the gall- 

 makers add greatly to the usefulness of the book, and 

 the typography is excellent. It is, in a very literal 

 sense, indispensable to all students of galls, while 

 those interested in the problems as to the nature of 

 living matter and its responses to stimuli will find in 

 its pages much matter for further investigations. 



ELECTRICITY ON THE FARM. 

 Electricite agricole. By A. Petit. Pp. 424. (Paris : 



J. B. Bailliere et Fils, 1909.) Price 5 francs. 

 ' I 'HIS book is one of the sixty volumes of the 

 -'■ "Encyclopedic agricole," published under the 

 editorship of M. Wery, the scope of which is well 

 summed up in the introduction : — 



" Extraire de notre enseignement superieur la partie 

 immcdiatement utilisable par I'exploitant du domaine 

 rurale et faire connaitre du meme coup a celui-ci les 

 donnees scientifiques definitivement acquises sur les- 

 quelles la pratique actuelle est bas6e." 

 It is in no sense a popular exposition of the principles 

 of electricity, but is rather written for the intelligent 

 farmer who knows something about electricity and 

 also about engineering, and is enterprising enough 

 to investigate the merits of a new suggestion. 



The first chapter is devoted to a recapitulation of 

 the general principles and the system of units em- 

 ployed. No attempt is made to dispense with technical 

 expressions; "connaitre le vocabulaire d'un art, c'est 

 deja connaitre cet art." The modes of transforming 

 mechanical into electrical energy are then discussed 

 in a very interesting chapter, the sources of energy 

 dealt with being w-ater power, steam, oil, and wind. 

 Of all these wind would be by far the best if elec- 

 tricity had to be generated on the farm itself, but the 

 difficulties are considerable. .Attempts have been 

 made in this direction particularly by M. La Cour 

 in Denmark, whose trials are perhaps the most com- 

 plete yet made, and who has demonstrated the pos- 

 sibility of utilising wind if there is also some sub- 

 sidiary source of power. But the subject is by no 

 means exhausted, and the utilisation of the energy of 



