E. J. BUTLER 19 



early in 1879.1 It has been proved that the uredospores can 

 live long enough to stand such journeys, as they liave been 

 gorniinatod in Germany after coming from Mauritius tlirough 

 Engknd. Spore production is very copious and all parts of 

 the plant, as well as the ground and packings, would readily 

 become coutamiiuitcd on an infected estate. 



Citrus canker [Psendoinonas Citri) was introduced into the United 

 States about 1912, when it was first teen in South Alabama 

 and Florida. It came from Japan on stocks of Satsunia orange 

 or Citrus trifoliata. Its dissemination throughout the Gulf 

 States, wliere it is at present causing considerable alarm, was 

 effected on nursery stock, perhaps from centres in Texas. 



The chrysanthenuim rust reached Australia in 1901 on cuttings 

 inrported from England. It was carried in the uredo stage, 

 which alone occurs in England, and only this form had 

 been found in Australia when McAlpine published his " Rusts 

 of Australia " in 190G. Probably it owes its spread fiom its 

 original home i]i Japan entirely to the trade in living plants. 

 Cuttii>gs have also been accused of carrying several other 

 diseases. 



Probably a large number of parasitic fungi can be carried on tlic seed 

 of their host plants. A packet of purchased seeds examined 

 in Kew some years ago was found to contain spores of several 

 of the diseases of the plants to which tlie seeds belonged.^ 

 The leaf spot of celery is spread largely ])y the use of infected 

 " seed ," not less than 90 per cent, of samples of commercial 

 celery seed examined having been reported from Wisley to 

 be contaminated in 1911.^ The hollyhock rust is a]u)ther 

 example. It has been proved capable of living through the 

 winter on the persistent carpels, etc., around the seed. Oats 

 are said to have carried the crown rust of this crop to 

 Ecuador and the introduction of the same disease to Pusa has 

 already bucn referred to. Straw packing is, however, an 

 alternative j)ossibility in this case. 



1 Thisclton-Dyor, W. T. Q. J. M. S., 1S8U, i). I I'.l. 

 2Massee, G. "Text-book of Fungi," 1!K)(), p. 221. 



3 Chittenden, F. J. "A note on celery Icaf-siiot-di^icase," Ann. A2yi>licd Biology, 1, 1914 

 p. 204. ■ 



