CONSIDERATIONS OF ABNORMAL GALL-GROWTH. 83 



shown by the lower and matured gall remaining in its firm 

 condition alter being gathered, and the other one shrivelling 

 and contracting, as shown in the figure, the kind of furrow 

 round its base indicating the extent to which the soft tissues 

 have drawn in. A longitudinal section shows each gall to 

 possess a central larval chamber, the internal structure only 

 differing in the parenchyma (or raerenchyma) surrounding 

 the harder substance of the cell-wall, which is in its usual 

 state in the lower gall, being shrivelled into a hard mass in 

 the upper one, with the central cell still undeveloped in 

 consequence of its immature state when gathered. What 

 causes may have operated to give rise to this secondary 

 growth it is difficult to conjecture. The presence of the 

 larval cell shows the true gall nature of the growth, and that 

 it is not a simple vegetable excrescence; but the great 

 difficulty lies in the botanical point as to why the 

 parenchymatous tissue should in this case have had the 

 power of throwing out a growth from itself under Cynips 

 oviposition, which (if it has occurred before) is at least so 

 unusual as not to have attracted attention. 



One explanation (conjecturally) lies in the possible 

 presence of adventitious buds. These, as is well known, 

 may be produced on any part of the normal growths of the 

 tree, and usually where there are stimulating conditions, and 

 an insufficiency of the ordinary buds to (-arry on the plant 

 action. Should this have occurred nothing further than 

 oviposition would be necessary (or the formation of the gall; 

 but the bud presence is very problematical ; and a more 

 likely solution suggests itself in abnormal oviposition having 

 taken place in the lowest gall before its formative powers 

 were exhausted, and having caused it to throw out the new 

 growth instead of continuing its own. 



It seems to me, however, that in considerations of gall- 

 growth, whether the primary cause lies in injection of Huid, 

 or oval or larval irritation, there is a twofold effect of 

 oviposition to be observed ; one producing the larval 

 chamber — the gall proper ; and (frequently) a secondary 

 one, which usually gives the gall its characteristic form, but 

 which still preserves its vegetable powers and structure in all 

 essential points, and consequently may be modified by 

 circumstances or state of health of the plant. 



These distinct formations may be traced through the stage 

 of division in Andricus cinvalor, where the internal cap- 

 sule may first be found embedded in a solid cellular mass; 



