42 Scientific Proceedings^ Rof/al Dublin Society. 



It is proposed, therefore, to discard the generic name Nozemia, suggested a 

 few years ago for those species having paragynons antheridia only, and to re-nnite 

 in the one genus Phytophthora all ihe species hitherto described under that name, 

 irrespective of the types of antheridium which prevail in them. 



A classified list of the twenty-two species of Phytoplithora recorded up to the 

 present, with brief notes thereon, is furnished. 



The economic significance of the rot does not appear to be great. Supporting 

 heavily laden, drooping branches with props and attention to orchard hygiene are 

 suggested as preventive measures. 



EXPLANATION OF PLATES. 



Plate I. 



All drawings were made with the aid of a camera lucida at a time when the 

 oospores were practically ripe, and all are magnified 645 diameters. 



Fig. 



1. Sexual organs of F. Syringae in which the antheridium is amphigynous ; 



from a naturally rotted apple. 



2. The same as 1, from the same source, but with the much more common 



paragynous antheridium. 



3. Sexual organs with amphigynous antheridium of F. Syringae, originally isolated 



from diseased Lilac in Germany. 



4. The same as 3, from the same pure culture, but with paragynous 



antheridium. 



5. Sexual organs of F. Gactorum with amphigynous antheridium, from culture of 



Whetzel's organism isolated from diseased apple in America. 



6. The same as 5, from the same pure culture, but with paragynous antheridium. 



7. Sexual organs of F. Cadorum with amphigynous antheridium, from culture of 



organism isolated by iJewley from diseased apple in England. 



8. The same as 7, from the same pure culture, but with paragynous 



antheridium. 



9. Sexual organs of F. Cadorum with amphigynous antheridium, fronr culture of 



organism isolated from diseased pear, received fronr Osterwalder (Switzer- 

 land). 



10. The same as 9, from the sa.me pure culture, but with paragynous 



antheridium. 



11. Sexual organs of F. Cadorum with amphigynous antheridium, from culture 



stated to have been isolated by Peters from Cactus seedlings. 



12. The same as 11, from the same pure culture, but with paragynous 



antheridium. 



13. Sexual organs of F. Far/i with amphigynous antheridium, from culture stated 



to have been isolated by Peters from seedlings of Fagus sylvatica. 



14. The same as 13, from the same pure culture, but with paragynous 



antheridium. 



15. A sporangium of P. Sgringae from culture from Irish apple, showing the 



flattened apex. 



16. A sporangium of F. Cadorum fronr tuft of mycelium on apple, showing 



papillate apex. 



