338 



BACTERIA IN RELATION TO PLANT DISEASES. 



varieties to attack. He obtained lists of sensitive and resistant varieties from seven 

 growers. A study of these lists showed a very general agreement upon the following 

 varieties as very susceptible: 



Snowball, single white; 



Grand Lilas, single blue; 



La Tour d'Auvergne, double white; 



Duchess of Richmond, single red; 



L'Ornement de la Nature, single red; 



Orandates, single blue; 



Mirandolina, single white; 



De CandoUe, single blue; 



Princess hereditaire des Pays-Bas, single while; 



Grand Vainquer, single white; 



Mimosa, single blue; 



Alba Maxima, single white; 



John Bright, single blue; 



The following varieties were regarded by the same growers as resistant, or only slightly 

 susceptible : 



Pieneman, single blue; 

 Norma, single red; 

 Pucelle d'Orleans, single white; 

 Voltaire, single white; 



Argus, single blue; 



Bleu mourant, single blue; 



Willem I, single blue; 



Maria Catherina (Robt. Steiger), single red. 



These two lists are copied from Wakker's French paper published in Archives neer- 

 landaises. 



In 1906 two of the leading hyacinth growers of Holland, men who have been in the 

 business many years, were good enough to go through their catalogues and mark off for me, 

 independently, varieties "much subject" to Bacterium hyacinihi, and varieties "very resis- 

 tant," leaving those varieties unmarked which are intermediate in resistance, or about 

 which there might be a difference of opinion or a lack of exact knowledge. In this way I 

 obtained information concerning about 300 varieties. I have carefully compared the two 

 lists and find them flatly contradictory only in the case of three varieties — single red Pelissier, 

 single rose Maria Cornelia, and single white Iv'Innocence. There are, however, numerous 

 discrepancies, many varieties being marked + or o by one grower and left unmarked by 

 the other. This might mean either entire lack of knowledge, or difference of opinion. In 

 case it were disagreement we might assume either difference of behavior on the part of 

 particular varieties in the hands of different growers, something not improbable, or that 

 one man is a closer observer than the other. Of course if a variety is much subject to the 

 disease in one field and resistant to it in another, the observed resistance might be entirely 

 a matter of accident and not due to any strongly inherent peculiarity, of which one might 

 take advantage in cross-breeding or selection. Varieties to the number of 130 were marked 

 + or o by one or other of the two growers, 73 as much subject to the disease, and 57 as 

 very resistant. One grower reported 59 varieties "much subject" and 43 "very resistant," 

 the other reported 22 varieties "much subject" and 32 "very resistant." The agreements 

 are of greater interest. There are 26 of these, a number apparently too large to be purely 

 accidental. In addition it should be mentioned that a number of the older varieties, marked 

 + in one catalogue, are not included in the lists of the other dealer, but must at one time 

 have been grown by him, and may have been discarded on account of disease. The writer 

 started inquiries to determine this point and found this supposition correct. Including 

 these, also, the number of agreements is 35. 



The writer subsequently received a catalogue from a third large grower, a person well- 

 known in the trade for thirty years or more. This man marked 61 varieties "much subject ' ' 

 and 13 varieties "very resistant." The varieties concerning which this third grower is in 

 agreement with the other two growers are marked with an asterisk in the following table. 

 Respecting the other varieties in this table he makes no statement. He is in contradiction 

 with one or other of the two growers, never with both, respecting the susceptibility of three 

 varieties : Clio, single light blue; Obelisk, single yellow; and Czar Nicholas, double rose. 



He reported on 41 varieties not mentioned by the other growers, 5 being marked as 

 resistant. 



The varieties concerning which the two growers agree are included in the following 

 lists: The starred varieties represent the agreements subsequently received from a third 

 large grower. 



