? DICH^NA QUERCINA. 149 



Gall caused by ? Dichaena quercina, Fries. 



(Plates LXVII, LXVIII.) 



Position of gall. — On the trunk of Quercus lyeduncidata, in 

 Broomliam Park, Guestling, Hastings. 



This enormous swelling affords an excellent illustra- 

 tion of many sucli growths on oak, elm and other trees, 

 in parks, groves, gardens, and woods in many 

 localities. 



It is remarkable that these growths do not cause 

 any noticeable diminution in the height, vigour in 

 expansion, or scarcity of foliage of trees thus affected. 

 Apparently the galls are not detrimental to the well- 

 being of the trees. This, of course, is not unusual, 

 because very few oak galls (excepting such as monopo- 

 lise buds and catkins) interfere with the development of 

 the surrounding tissues ; a character more noticeable 

 in the galls on, and in, leaves, than in any others. 



As far as can be ascertained, without cutting 

 into this gall, it is composed of the same materials as 

 the other portion of the trunk. It is without holes of 

 any considerable depth, and apj)ears to be perfectly 

 solid. 



The bark, or cortex, is scabrous. Although very 

 similar in appearance to the bark of the trunk, it will 

 not peel off in the same manner. 



The scale shown in each plate is 30 cm. (= almost 

 12 in.) The dimensions are : 



Girth of trunk immediately beneath swelling . 7 ft. 10 in. 



Distance from groimd to top of swelling . . 6 ft. 3 in. 



Peripheral circumference of swelling . . .10 ft. 3 in. 



Girth of trunk and swelling at ec|\;atorial line . 11 ft. 10 in. 



The fruiting stage of all the species of the genus 

 Dichaena is rarely seen. Of some species it is not 

 known. Some species are common. All are true 

 parasites. 



