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NATURE STUDY NOTES 
PLANT “GALLS”—This is the name given to the 
unsightly swellings often seen on the branches of 
wattle trees, oaks, roses, etc. They are caused by 
a great variety of insects and mites—the former 
usually one of the Hymenoptera (see p. 8). They 
are produced by the dividing of the plant tissues, 
usually in the cambium layer, which is brought 
about and developed by the presence of the insect 
larva. One or more eggs are laid in the plant tissue 
by the insect, and the larva from each exudes a 
secretion which cortibines with the plant juices. 
This has the effect of transforming the growth of 
the plant cells, so causing division and malforma¬ 
tion of the plant tissues that produce the swellings 
or “galls.” 
Printed by Whitcombe and Tombs Limited g6 65 
