688 NOTES ON THE NATIVE FLORA OF N. S. WALKS, X., 



Tt is usual, of course, for both valley and height to produce 

 trees, the differences in soil accounting perhaps for different 

 local species, but this does not apply to the Canberra Plains, 

 which, for some unexplained reason, are for the most part tree- 

 less, though all the considei-able elevations around are clad with 

 forest-growths. 



Insect Action on Twigs and Buds. 



Some gouty swellings were found at the Cotter River on fruit- 

 ing twigs of Encalyptus hcemaatoma (Brittle Guni), which, Mr. 

 W. W. Froggatt, F.L.S., informs me are caused by the attack 

 of small chalcid wasps (Chalcididse), some of wiiich are plant- 

 feeders and deposit their eggs just under the bark. The effect 

 on these twigs was such that, in some cases, for a length of 15*3 

 cm. (about 6 J inches), they had been increased in diameter from 

 2"5 mm. to 16 cm , or about 6^ times their original diameter. 



In November, 1911, great numbers of very interesting insect- 

 galls were found within the City site on manv trees of Euca- 

 lyptus dealhata (Red Gum). The flower buds were aborted by a 

 dipterous larva which Mr. Froggatt has kindly identified as 

 belonging to the family Agromyzidae. By the action of these 

 larv£e, the buds had been increased in diameter from 2 mm. to as 

 much as 1'2 cm., or six times their original size (Text-fig. 2). In 

 some cases, five out of six buds in the umbel were affected. The 

 effect of this swelling of the buds so greatly increased their 

 weight, that broken branches were to be seen in many directions, 

 reminding one of the result of a snow-storm. 



Plants absent from the Federal Territory. 

 Owing largely to climatic reasons, several groups of plants 

 are absent from this district, the locality being too cold for 

 them, though, in more northern latitudes, they may ascend to 

 greater elevations than 2,000 feet. No species of Angophora, 

 the coastal Apple-Tree, was seen, and its absence from the south- 

 western district was commented upon by Hume and Hovell, in 

 their overland-journey in 1824 {ibid., p.87).* No representative 



* For previous remarks in regard to distribution of this species, see 

 these Prooeediugs, 1905, xxx,, p. 207. 



