EOCAL YPTUS. 37 



have the trees killed by the repeated destruction of the 

 leaves in the same season thus giving the tree no oppor- 

 tunity to recuperate. The blue gum however has not been 

 reported to have been destroyed by the cicadae. Consul 

 Baker reports from the Argentine that the Eucalyptus is 

 the only tree introduced to the wide plains of that Repub- 

 lic not destroyed by locusts. 



The borers attack Eucalyptus viminalis more than any 

 other tree. From their punctures exudes a sweet, amorphous 

 and whitish substance, much prized by the natives. From 

 this mellitose substance the viminalis has obtained the name 

 of manna gum. When this manna is found in comb -like 

 pieces on the ground it is quite a pleasant sweet. We 

 could doubtless obtain this manna by instrumental punc- 

 tures. It is not the same as the true orcus-manna as John- 

 ston's* Australian analysis shows, Ci2 Hi4 OH, and the quan- 

 titative analysis of viminalis manna by Anderson is sugar 

 49.06, gum 5.77, starch 4.29, inulin 13.80, cellulose 12.04, 

 water 15.01. This manna falls also from Eucalyptus oleosa 

 and Eucalyptus odorata and occasionally from other Euca- 

 lypti but never to anything like the same extent as from 

 Eucalyptus viminalis. I have only once seen manna on a 

 gum tree in California. This was on Eucalyptus viminalis 

 at Santa Monica Heights. 



In mentioning these insect injuries to various species of 

 Eucalyptus it is only proper to say that this genus has so 

 far proved practically free from injurious insect effects 

 wherever it has been introduced. Its introduction by seed 

 alone has prevented the introduction of its Australian ene- 

 mies and no exotic enemy of moment has thus far ap- 

 peared. I may say, too, that in my own wanderings in 



* From Von Mueller. 



