September 5, 1895] 



NA TURE 



435 



plain and tlie station was allowed for, and it was found 

 that this correction brought the g^ravity at each station 

 much nearer to the computed value for the latitude than 

 either of the previous inethods. The conclusion was that, 

 when large areas were considered, they were approxi- 

 mately in isostatic equilibrium. "The result of this series 

 [of observations] would therefore seem to lead to the 

 conclusion, that general continental elevations are com- 

 jiensated by a deficiency of density in the matter below 

 sea level, but that local topographical irregularities, 

 whether elevations or depressions, are not compensated 

 for, but are maintained [supported] by the partial rigidity 

 of the earth's crust." (Putnam.) "The measurements of 

 gravity appear far more harmonious when the method of 

 reduction postulates isostacy, than when it postulates high 

 rigidity. Nearly all the local peculiarities of gravity admit 

 of simple and rational explanation on the theory that the 

 continent as a whole is approximately isostatic, and that 

 the interior plain is almost perfectly isostatic." (Gilbert.) 

 It appears therefore that the crust of the earth is 

 sufficiently thick and strong to carry such unequal loads 

 as considerable mountains upon its surface without 

 necessarily breaking through ; but, when a large area is 

 involved, it bends downwards into a denser material 

 beneath, so that the crust and the load it carries are 

 conjointly in approximate hydrostatic equilibrium. 



O. Fisher. 



SOME RECENT BOOKS ON MYCOLOGY. 



British Fii/ii^iis-Flora. A Classified Text-book of Myco- 

 logy. By George Massee. Vol. iv. 8vo, pp. viii. 522. 

 (London and New York : George Bell and Sons, 1895.) 



Systematic Arrangement of Australian Fungi, together 

 with Host-Index and List of Works on the Subject. 

 By Dr. McAlpine, Government Vegetable Pathologist. 

 4to, pp. vi. 236. (Melbourne: Robt. S. Brain, Govern- 

 ment Printer, 1895.) 



Guides to Growers. No. 18. Onion Disease. By D. 

 McAlpine. (Victoria : issued by the Department of 

 Agriculture, 1895.) 



MR. M.A.SSEE is to be congratulated on the comple- 

 tion of another volume of his " British Fungus- 

 Flora." There has been no complete work of the kind 

 issued since the publication of M. C. Cooke's " Handbook 

 of British Fungi" in 1871, and the knowledge of these 

 obscure plants has advanced enormously since then. In 

 the first three volumes the author treated the Basidio- 

 mycetes and the Hyphomycetes ; the present volume takes 

 up the large natural order of the Ascomycctes, and deals 

 in turn w4th three families — ^the Gyinnoascacea, the flys- 

 teriaceie, and the Discomycctes. The ffysteriacea: form 

 such a natural transition between the Discoinycetes and the 

 Pyrenoinycetcs, that it seems a pity Mr. Massee has not so 

 arranged the families as to make them follow each other 

 in the text-book ; he has, however, very carefully pointed 

 out the atifinities of the different groups. 



A general account of the Ascomycetes, their life-history, 

 habitat, &c., is given in the introduction. The author 

 agrees with Brefeld that sexual reproduction is unknown 

 in this family. There is also some useful information 

 about the best methods of collecting and preserving speci- 

 NO. 1349, VOL. 52 1 



mens, and of examining them. New descriptions have 

 been written out for many of the plants, based in nearly 

 every case on the author's own observations. Wherever 

 it has been possible, he has examined the type specimens, 

 or those specimens accepted as authentic in well-known 

 exsiccati. It is impossible to over-estimate the value of 

 such work. The descriptions are full and complete, and 

 great care has been taken to give careful measurements. 



The HysteriacecE have not before been worked up for 

 Britain. Mr. Massee has not included Acrospcrmum in 

 this family, nor in this volume. We await the next instal- 

 ment of his work, to see where he will place it. 



" British Discomycetes," by Mr. W. Phillips, has been 

 for some time the standard work for that family. It was 

 published in 1887, and there has been no reason for any 

 material change in the way of treating the subject. The 

 genera Xylographa, Biatorella, and Abrothallus, pre- 

 viously included among lichens, have been proved to be 

 fungi, and are recorded, Xylographa in the family of the 

 Phacidea, Biatorella and Abrothallusm ih.^ Patelliarii^. 



The classification of the fungi is pretty well fixed as 

 regards the natural orders, but no two systematists are 

 agreed on the arrangement of genera and species. 

 What characters are important enough to constitute a 

 genus, is a question that each one answers in his own 

 way. Phillips gave great importance to microscopic 

 characters, but he was also largely guided by features 

 visible to the naked eye or on slight magnification. He 

 has comparatively few well-marked groups, and somewhat 

 large genera with sub-genera. Saccardo laid much more 

 stress on the differences between the species, and created 

 new genera to represent deviations from the types, or 

 revived old genera that had been sunk by systematists 

 like Phillips. Mr. Massee goes even further ; he retains 

 nearly all the genera that had been kept up by .Saccardo, 

 and he has added in the Discomycctes eight genera revived 

 from older authors, and five new genera, none of these 

 being founded on new plants. Mr. Massee may be right 

 in his views of classification, but the multiplication of 

 genera and species, where that can be avoided, is much 

 to be regretted. The matter has been admirably stated 

 by Mr. Spruce in his " Hepatica; of the Andes and 

 Amazon," p. 73. "For a local flora," he writes, "or a 

 limited area, too many genera will tend to produce con- 

 fusion rather than precision, especially where several of 

 the genera are monotypic ; so that, on the whole, it seems 

 desirable to make our genera as comprehensive as pos- 

 sible." There are several monotypic genera included in 

 this volume, as for instance Citbonia, to which genus 

 Ascophanus Boudieri has been transferred on account of 

 its globose spores, those of Ascophanus being elliptical. 



The task of classifying the Pezisce is no light one ; 

 they are here divided into three large groups — Glabratcc, 

 Vestitce, and Ctirnosa-, under which the genera and species 

 are arranged in a way that differs, in many instances, from 

 that of every previous writer. The two first groups arc 

 familiar to us as the Nudes and Vestitee of Phillips. In 

 the latter group the genus Lachnclla has been dropped, 

 and the species are dispersed and reclassified under 

 Erinella, Echinella, Diplocarpa, Dasyscypha, &c. f^ach- 

 nella Cupressi has been placed by itself in the genus Pitya, 

 because the margin is free from the external hairs that 

 are so marked a feature of this group, and because it 



