WILT-DISEASES OF TOBACCO. 263 



to cultivate two, and if need be three, types which are continually kept for the same kind 

 of soil. This is directly opposed to the principle of "blood-refreshing." As it is agreed 

 that in this "blood-refreshing" the habitat and the climate have influence on the charac- 

 teristics of the offspring, something which is not proved but which we grant for the moment, 

 why should one use seed from a hill plantation which always has sufficient, sometimes too 

 much, rain, for cultivation on the coast where the tobacco stands every chance of being 

 obliged to go through a long period of drought ; that does not seem to be logical. 



If from the Deli tobacco several types can be isolated, and this seems probable, never- 

 theless one must not suppose that they will be precisely alike in their ability to endure 

 drought or much moisture. Should not something be established in this direction on the 

 coast plantations, where all the growers are again complaining? 



What has been said here about selection in general is also of value in regard to the selection for 

 the purpose of obtaining a race more resistant to the slime-disease. Also in this connection one will 

 do well to take into consideration the kinds of soil. What will happen I can not assert, but the 

 possibility is not excluded that some one will obtain a more resistant race which is of no value for 

 his neighbor who has different soil, and is perhaps still more susceptible than that which he has been 

 accustomed to plant formerly. 



What makes this selection difficult is the fact that one can never see in a plant what he has there, 

 although always its value as a seed-plant can be judged the following year in the descendants just as 

 leaf-production is best judged in the curing-house. Two plants of similar height, with exactly the 

 same number of leaves of about the same length and breadth, in short, plants which every one would 

 consider equally valuable, may bring forth offspring which differ to an important extent. A plant 

 with 30 leaves may belong to a family which brings forth on an average 30 leaves, but it may also be 

 an exceptionally fine specimen of a family which produces on an average not more than 25 or 26, or, 

 finally, an inferior example of a family which averages ^ leaves per plant. All this indicates the 

 necessity of sowing separately purely pollinated seed from each plant. In such pedigree-cultures two 

 or three years must elapse before we know whether the selected lines are constant. This affords the 

 great advantage of comparing pure lines with the ordinary crop for two consecutive years, not only 

 in the field but also in the curing-house. 



AMERICAN STUDIES OF THE SUMATRAN ORGANISM. 



Through the courtesy of Dr. Honing the writer received cultures of the Sumatran 

 tobacco organism in the summer of 19 13. One was sent direct, another via Amsterdam, 

 where the original tube was retained and a transfer sent on. Later a third came direct. 



The three cultures reached Washington in good condition and proved infectious to 

 tobaccos, on which the external signs and the tissue disorganization could not be distin- 

 guished from those due to the North American tobacco-wilt organism. Black stripes 

 appeared on the stems, with yellowing and irregular drying-out of the leaves, the vessels in 

 which were stained black and filled with the bacteria, especially those of the mid-rib. In the 

 sections which I saw, the bacteria were confined to the inner wood, in which bacterial 

 cavities had formed. Some of these sections were made 5 or 6 inches from the needle pricks. 



Up to the end of the sixth week (when the first experiments were broken off) the be- 

 havior of this organism in our tubes of milk and litmus milk corresponded closely to that of 

 the Granville tobacco-wilt organism, i. c, there was no development of acid or separation 

 of the casein, but only a progressive bluing of the litmus.* 



Subsequently one of our stocks of litmus milk reddened. I thought at first that the 

 reddening of the milk was due to an unsuspected acid-forming anaerobe, which was not 

 killed by the steamings, and which was unable to make its presence visible except under the 

 protecting influence of some active aerobe, such as Bad. solanacearum. With this in mind 

 we made tests in deep tubes of agar in the following way : Stabs were made the whole length 

 of the agar from litmus milk which had been inoculated with the Medan organism and which 



*Plain milk tube-cultures 7 weeks old were translucent and brownish. In another set a pencil could be seen behind 

 those 8 weeks old, although the casein was not precipitated. 



