BOOK REVIEWS. 



517 



you do not know where to look. The present classification is there- 

 fore neither scientific nor popular. 



No mention is made of the usual classification of the makers of the 

 galls, nor is any figure given of even one species. This is a great 

 omission in a work of this description. Both in Cameron's " Phytophagous 

 Hymenoptera " and Stratton's translation of Adler's monograph of 

 ''Alternating Generations in Oak Gall Flies," which up to the present 

 time have been the most accessible works on Oak galls, the galls are 

 classified under the names of the insects which emerge from them, and 

 are arrauged according to their natural affinities, which is very much 

 better and more convenient. In a popular book, a list of the galls 

 arranged under the heading of the part of the plant on which they may 

 be found should also be given. 



In quoting various authors as to the meaning of the word "cambium " 

 (the layer of tissue in the plant in which the gall flies deposit their eggs), 

 the definition given in Dr. B. Daydon Jackson's recent " Glossary of 

 Botanic Terms " is omitted, though it is one of the best, namely " A layer 

 of nascent tissue between the wood and the bast adding elements to both." 



Chapter 5 is devoted to a very interesting account of the British Oak, 

 the Turkey Oak, and the Evergreen Oak. In chapter 6, hints are given 

 on collecting and mounting Oak galls, and the implements required are 

 enumerated. A pair of sharp nippers, a figure of which is given, is 

 said to be essential, but we should have thought that a pair of scissors 

 with one curved blunt blade and one sharp one, such as are so frequently 

 used in gardens, or one of the pruning implements generally known as 

 " secateurs," would prove much more convenient for the purpose than 

 the wire cutters used by the author. A white cloth would in many cases 

 prove more useful than a sheet of paper ; it would not tear or blow 

 away so easily. There is a clerical error on p. 43, the word " blur " is 

 used instead of " burr." The descriptions of the galls are given in a very 

 clear and concise manner in a synoptical table in every case. 



Three galls (if they can be considered galls) are described and figured 

 which are not formed by members of the family Cynipidae. One of the 

 Coccidac or scale insects forms slight pits in which it lives on the 

 Oak shoot, but it is not the cause of more than a very slight swelling of 

 the shoot, and the insect is not hidden in the stem, so there is nothing 

 that can really be called a gall. 



The grubs of one of the "gall-gnats " cause the lobes of the leaves to 

 fold over them, and under this protection the grubs live and feed, but there 

 is no gall. 



The third gall is caused by a fungus, Dichaena quercina, which infests 

 the stems, branches, and even twigs, causing smooth rounded swellings o 

 the bark, and on a longitudinal section being made it is found that the 

 wood to some depth is implicated. It is very questionable if the tumours 

 on the oak stem (see plates lxvii. and lxviii.) are caused by this fungus. 

 Similar excrescences are very common on the stems of other trees 

 whose branches and shoots do not show any signs of being attacked by 

 this parasite. 



The plates are as a rule very good ; that showing sections of the 

 stem of an oak would have been more interesting had a diagram been 



