488 Scientific Proceedings, Royal Dublin Society. 



various places in Ireland, showing that the disease must be fairly widespread 

 here. We now have reason to believe that the disease also occurs in England. 

 Subsequent to the discovery of the parasite which causes the disease, 

 cases of attack on Asters and Petunias by the same or a very similar organism 

 were met with ; and the scope of the investigation was extended to include 

 such cases. Some account, therefore, of this part of our work is included in 

 the present communication. 



II. — Symptoms of the Disease. 



The disease is usually first fully apparent when the young affected plants 

 are about six inches high. In certain cases, however, it can be recognized in 

 much younger plants, while in others the attack may not become obvious 

 until the plants are considerably older. 



It is characterized by the appearance of a brownish or blackish discolora- 

 tion of the external tissues of the stem at or just above ground-level. These 

 tissues become more or less shrivelled and destroyed, and sooner or later the 

 top-heavy stem of the young plant falls over. 



At first the foliage of the young plants does not usually show any charac- 

 teristic symptoms of disease. Even on plants which have already toppled 

 over, the leaves may remain green and turgid for a time, this being clue to 

 the fact that the upward passage of sap through the woody tissue of the stem 

 is not all too seriously curtailed at the outset. As time goes on, however, the 

 margins of the leaflets begin to roll upwards and inwards, the leaves turn 

 yellow and finally die. 



Occasionally, but not frequently, the foliage becomes flaccid or wilted 

 before yellowing and death occur ; but, strictly speaking, the disease is not 

 one of the " wilt " type, and it is not one of haclro- or tracheo-mycosis such 

 as occurs in tomato and potato plants when attacked by Vcrticillium albo- 

 atrum (7). 1 



If an affected plant be lifted carefully from the soil, it is found that the 

 rotting of the tissues at the base of the stem is continued downward into its 

 underground portion and also into the root system. This, however, is the 

 reverse of the direction in which the rot actually proceeds ; for it starts in 

 the roots, as a rule, works its way upwards for a short distance into the stem, 

 and then usually ceases just above soil-level. 



The cessation of the rot at this point is generally a decided one, and is 

 perhaps due to changed moisture conditions. It may be stated here that if 

 young plants which are not too far gone be cut off above the region of decay 



1 The figures in brackets refer to the bibliography at the end of the paper. See p. 503. 



