August io, 1905] 



NA TURE 



)J9 



states should be connected up in the (/),t') plane by a 

 system of curves T = constant, consistent with the dif- 

 ferential equation 



dv 



'i/P' 



and making- y,, equal to the specific heat at constant 

 volume in the re^rions which represent physically 

 possible states. For the validity of the rule it does 

 not matter how the curves are joined up provided that 

 the above differential equation is everywhere satisfied. 



The notation may appear somewhat cumbersome, 

 but anvone who tries to e.xpress thermodvnamical 

 formulae in writing" will find it impos^ibIe to do so 

 clearly and precisely without some such large array of 

 symbols. In particular, the use of capital letters 

 for the volume, entropy, energy, and other thermo- 

 dynamic magnitudes of a whole body, and small 

 letters for the corresponding magnitudes per unit 

 mass, is a very useful convention. The different 

 forms of d. 5 used for differentiations, variations, 

 and diminutions are less easy to follow. If we 

 attempt to compare the subject of this volume with 

 Prof. Planck's excellent little treatise, we shall prob- 

 ab!v come to the conclusion that Prof. Voigt goes 

 more into elaborate details, while Prof. Planck keeps 

 more to the main points. The book now before us 

 thus contains the more information about a wide range 

 of phvsical phenomena, but Prof. Planck's book is the 

 easier to read. Neither book can be said to be better 

 or worse than the other, as each has its own uses. 



The French translation, which forms No. 22 of the 

 physico-mathematical series appearing under the title 

 of Scienlia, contains the two papers " Graphic 

 Methods in the Thermodynamics of Fluids " and " A 

 Method of Geometric Representation of the Thermo- 

 dynamic Properties of Substances by Means of .Sur- 

 faces," both originallv published in the Connecticut 

 Transactions for 1S73. I' '^ accompanied by a short 

 notice of Gibbs's life and works, and an introduction 

 bv Prof. Brunhes. The latter, giving as it does a 

 general and explanatory account of the subject-matter 

 of the papers translated, forms a useful addition to 

 the book. G. H. B. 



FUNGUS-GALLS. 



Bcifriigc ziir physiologischen Anatoinie dcr PUzgallcn. 

 By Hermann Ritter von Guttenberg. Pp. 70; with 

 4 plates. (Leipzig: W'ilhelm Engelmann, 11)05.) 

 Price 2s. qJ. net. 



THE study of galls is never more profitably 

 approached than when the mutual inter-reactions 

 between parasite and host-plant are considered con- 

 jointly. The intimate connection existing between 

 these two, whether the parasite be insect or fungus, 

 forbids the divorce of either party, and it is therefore 

 a pleasure to come across a work in which this close 

 union is recognised, and an endeavour made to ex- 

 plain the anatomical changes occurring in fungus- 

 galls from a physiological standpoint. 



In this work the effects caused by five different 

 fungi on as many host-plants are described. The 

 fungi all belong to separate families, as also do the 

 NO. 1 867, VOL. 72] 



hosts, and the series is therefore admirably suited for 

 generalising the results. It includes Albugo on 

 Capsella, Exoascus on Alnus, Ustilago on Maize, 

 Puccinia on .Adoxa (where, however, no gall-formation 

 arises), and Exobasidium on Rhododendron. 



The consiancv of form and complexity of structure, 

 characteristic of many insect-galls, are not found here, 

 and the principal changes observable may be briefly 

 summarised as consisting of the hypertrophied de- 

 velopment of a large-celled, thin-walled parenchy- 

 matous tissue containing very vacuolated protoplasm, 

 enlarged nuclei, and rich stores of starch or water. 

 This is accompanied by an increase in the number of 

 vascular bundles, or at least of their elements, and by 

 modifications of the epidermis, whilst the assimilatory 

 and aerating systems generally tend to be suppressed. 

 These anatomical changes are, in the author's 

 opinion, mostly due to a change of function which 

 the tissues assume under the influence and for the 

 exclusive benefit of the parasite. The fungus may 

 almost be regarded as a sculptor working with clay. 

 It moulds the host-plant at will, forcing it to lay down 

 a store house and fill it with food for the tenant's 

 use, forcing the xylem to predominate when water is 

 needed, or the phloem when carbohydrates are re- 

 quired. Where spore formation is proceeding, 

 accessory bundles are laid down to provide the in- 

 creased supplies necessary. Here the epidermis is 

 weakened so as not to hinder the dispersal of spores, 

 there the mechanical tissue suppressed lest the pro- 

 gress of the fungus be impeded, while even the 

 chlorophyll granules, when present, work in the 

 service of the parasite. Everywhere the story reads 

 as if the host had become wholly subservient to the 

 will of the parasite ; but were the author now to ex- 

 change his brief Jind act as counsel for the host, he 

 might equally well explain many of the changes as 

 evidencing an intense effort put forth by the latter 

 to overcome the former. .-V final summing up would 

 then be less partial, and productive of still more 

 valuable results. 



Here and there the author has observed indications 

 of this struggle, and one point to which he directs 

 attention is of special interest, viz. the deposit of a 

 cellulose cap or sheath around the invading haus- 

 torium or hypha, apparently for the purpose of pre- 

 venting its entry. This phenomenon, which, though 

 of frequent occurrence, is not generally known, is 

 most remarkable in Ustilago Maydis, where the whole 

 length of an intracellular hypha in its passage 

 through a cell may become enclosed in a cellulose 

 tube. Subsequently this tube may become irregularly 

 thickened in parts, and then shows distinct stratifi- 

 cation. 



The observations regarding the behaviour of the 

 nucleus — its lobed appearance, occasionally leading on 

 to amitotic division, its participation in the formation 

 of the above mentioned cellulose sheath, its subse- 

 quent decrease in size, the aggregation of the chro- 

 matin at the periphery, &c. — are all most interesting. 

 Some of them need confirmation by more exact histo- 

 logical methods than the author seems to have 

 emploved, before his conclusions can be accepted, e.g. 



