PLANT GALLS 



373 



research, and the breeding and preservation of gall insects. The 

 second part consists of a descriptive index of galls arranged 

 botanically, not under families, but in alphabetical sequence of 

 the genera. This arrangement ensures easy reference and at the 

 same time serves to curtail the index, but it has some obvious 

 disadvantages. 



There are ten excellent black-and-white plates, with numerous 

 figures, chiefly of familiar galls, drawn from nature by Dr. G. 

 Dunzinger. An illustration of special interest depicts the curious 

 and little known conical projections which occur on the hymenial 

 surface of woody fungi, particularly Fomes applanatus. They are 

 situated near the margin, are from 5-10 mm. high, and each has 

 a central cavity. Dr. Eoss appears to be in doubt as to the 

 causation of these tubercles, but I think that Kiedel discovered in 

 1900 that they result from the presence of the larvffi of a Dipteron 

 belonging to the genus Ditomyia, species at present unknown. 



The galls which arise from the presence of the larva? of the 

 gallwasp, Neroterus osteus, in the midrib of oak-leaves are poorly 

 represented in Tafel vi. 134-136. They are of special interest 

 because of their remarkable abundance during the past summer 

 throughout the south of England. They were the cause of 

 the very noticeable marginal discoloration of the leaves, which 

 was so frequently, though quite erroneously, attributed to the 

 drought. 



In Tafel i. fig. 12 we have a magnified view of the hairs which 

 arise in the axils of the leaf-veins of ^sciclus Hippocastanum, 

 through the presence of the mite, Eriophyes Hippocastani Fockeu. 

 The leaves of the horse chestnut are usually remarkably free from 

 galls. Three species of mites give rise to pubescence on the leaves 

 and inflorescence, and an unknown cecid is said to cause minute, 

 hemispherical, brown bodies to appear (rarely) on the lower 

 surface of the leaf. These are at present the only European 

 records. It is well known that the leaves of the horse chestnut 

 are quite exempt from attack by leaf -mining larvse. The com- 

 parative absence of galls from the leaves of certain trees is a 

 subject of great interest, deserving special investigation. 



The inclusion of galls caused by fungi makes this work a 

 valuable companion to Howard's monumental volume on Les 

 Zoocecidies des Plantes d'Europe. Amongst those that are 

 delineated are the remarkable outgrowths on the female inflores- 

 cence of the common alder caused by Ascomyces alnitorquus, and 

 a "witches' broom" on birch attributed to the presence of 

 Ta2}hi'ina turgida. 



It is pleasing to find but few changes in nomenclature. It 

 may be noted that Chermes (Adelges) strobilohius, which is asso- 

 ciated with the little greenish pineapple gall on the common 

 spruce, is now placed in the genus Cnaphalodcs. 



Dr. Eoss may be congratulated on having produced a text- 

 book which will be of great value to European cecidologists. 



E. W. S. 



