Workers in Plant Tissues. 



The position she always finally selects is a bud, not 

 a flower-bud, but one that should under ordinary con- 

 ditions produce a twig and leaves. This bud she 

 proceeds to prick with her sharp-pointed ovipositor 

 in three places, in the most systematic manner. The 

 three spots in the bud selected for piercing by the 

 Gall-fly are just the three points where the rudiments 

 of leaves exist, and these, instead of developing into 

 leaves, by their changed mode of growth give rise to 

 the bedeguar or gall. Usually this gall is of large size, 

 handsome in colour, and if cut open will be found to 

 contain numerous cells, each the nursery of a tiny 

 larva ; but imperfect specimens are by no means un- 

 common, such as a small one seated on a full-grown 

 rose leaf, and these, it is thought, are due to the failure 

 on the part of the parent insect to complete the prick- 

 ing operation. These rose galls often contain, in 

 addition to the rightful inhabitant, other larvae that 

 have emerged from eggs placed in the tissue of the 

 perfect gall by one or other of the parasitic Gall-flies. 



The oak is a particular favourite with the Gall- 

 flies, and produces in consequence a number of dif- 

 ferent shaped galls. On the under surface of the 

 leaves are to be found quantities of the so-called spangle 

 galls oval, flat bodies that in size and shape resemble 

 the metallic discs called spangles ; the oak apple is 

 another form familiar to most people ; and a third 

 type, called currant galls, are equally well known. Ex- 

 periments carried out with a view to finding out the 

 particulars of the life history of some of these oak- 

 frequenting/ Gall-flies have brought to light many 

 interesting points, and proved beyond doubt that 



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