THE 0ENUS EtJCALYPTUS. 219 



box, so that an intermediate variety springs up. And it is a 

 curious fact, that in some districts where these trees prevail, there 

 is a species which in appearance sometimes resembles the one, 

 and sometimes the other. Upon careful examination, I find that 

 whilst the young trees look very like the box, and the older 

 approach the grey gum, the seed vessels of this tree differ from 

 those of the box, in being usually five celled, and from the grey 

 gum, in having the valves inserted. With respect to hybridization 

 in this genus, the flowers of which are probably fertilized before 

 the operculum is cast off, Dr. P. Mueller does not think that it 

 is impossible, but that all ordinary chances are against it. " Still," 

 he continues, "as Mr. W. S. Macleay remarked, parrots and 

 other birds occasionally bite off the flower-buds, and, may 

 accidentally uncover a stigma, and remove the anthers ; and 

 again insects may then finish off their work and carry pollen 

 across from another species. But then hybrids are barren, as a 

 general rule and how few seedlings can spring up of such 

 hybrids, compared with the ordinary young plants of the pure 

 species." My own impression is, that the varieties of the grey 

 gum, to whatever causes they may be due, are not transmissible 

 from generation to generation, and that they do not extend 

 beyond the individuals so circumstanced ; whilst I regard one of 

 the kinds at least, which workmen consider hybrid, as a true 

 species, for it has a uniform seed-vessel of its own, and prevails 

 to too great an extent to admit of the supposition that it is the 

 result of fortuitous impregnation. The diseases and age of 

 Eucalypti, are subjects also of great interest, but as yet they have 

 received only a moderate share of attention. E. globulus, or 

 "the Tasmanian Blue G-um," when removed from its native soil, 

 is subject to the ravages of beetles, and many trees in New 

 South Wales have perished from that cause ; but the most 

 remarkable instance of disease amongst our gums in this 

 colony, is the fact that in some districts, whole forests of trees, 

 covering many square miles, have sickened and died without any 

 apparent cause. Some persons attribute the disease to drought, 

 and some to floods, whilst again others think that during excessive 

 rains, a grub or fungus has been generated in the low lands and 

 gradually spread to the trees on the higher ground.* I confess 

 * Sir Thomas Mitchell mention!', that Regent's Lake, which was visited by 



