182 



gist will find it impossible to classify by the means of such 

 smaller sub-divisions." (Sir Rod. Murchison, Siluria, p. 

 51.) 



Ideal Distribution of Genera in Time from independent or 

 widely-separated, geographical centres. 



On the hypothesis that all organic genera did not arise and 

 radiate repeatedly from one geographical centre only, and 

 that a considerable space of time would be consumed in the 

 greater extremes of distribution as regards terrestrial plants 

 of higher organisation, the following diagram is designed, 

 roughly illustrating the possible complication arising out of 

 the radiating distribution of genera from widely-separated 

 centres ; and also illustrating the different nature of the 

 possible associates to be met with at different stations should 

 the survivals succeed in reaching a middle station or the 

 antipodes of the place of their generic origin. 



The cross dotted lines indicate the possible lapse of 

 geological time between the commencement and close of the 

 migration of each genus, and also the curious interweaving 

 of different genera which originated in centres widely 

 apart. 



NOTES ON A RECENT CASE OP POISONING CAUSED 

 BY THE EXHALATION OP RHUS RADICALS 

 (TOXICODENDRON) AT THE BOTANICAL GAR- 

 DENS, HOBART. 

 By P. Abbott, Supbeintbndent Botanical Gardens. 



A very peculiar case of poisoning, caused by plant exhala- 

 tion, having occurred at these gardens, it is desirable that it 

 should be recorded, not alone for general information, but 

 more especially as it is possible that the plant in question 

 may, to a limited extent, be under cultivation in other places. 



Before describing the case, a few general observations 

 relative to the matter may not be out of place. 



The genus Rhus embraces numerous species, many of which 

 produce gums and resins used in the manufacture of superior 

 kinds of varnish. R. verincifera yields the very best japan 

 varnish ; others are lich in tannic matter, and are esteemed 

 for the preparation of leather, while not a few of the species 

 are poisonous to a greater or less degree, R. pumila, of Upper 

 Carolina,, being the most pernicious of them, A case is 

 reported where the mere gathering of seeds from this species 

 resulted in the poisoning of the whole body, and produced 

 lameness, which lasted for a considerable time. Rhus 



