156 BACTERIA IN RELATION TO PLANT DISEASES. 



strata the lemon-yellow organism did not come up at all; only contaminating organisms 

 appeared. The citron-yellow colonies were obtained, however, by stirring a small amount 

 of the slime from diseased plants into a drop of sterile water on a sterile cover-glass and trans- 

 ferring this to slices of sterile potato lying in glass dishes. By making several parallel 

 streaks, one finally obtains pure cultures. The first streaks contain bacteria in great num- 

 bers; the last, on the contrary, only isolated colonies. Some of the latter were lemon-yellow 

 colonies of an organism agreeing in all respects with that found on the diseased plants. 



The isolated bacterium, and also that examined from the plant, is short-ellipsoidal, 0.66 

 to 0.99^ long and slightly less wide. It has a distinct capsule both on media and in the plant 

 and is non-motile in hanging drops made with organisms from both sources. It stains with 

 Loffler's methylene-blue, with carbol-fuchsin, and with Gram's stain (both sources). It is 

 not acid-fast (both sources). When treated with iodine solution there is no granulose 

 reaction, either with slime taken from the plant or with pure cultures. No spores have 

 been observed. In fluid media, like bouillon, decoction of Dactylis glomerata, with and with- 

 out peptone, there forms in the course of 7 days, on the surface of the liquid, an interrupted 

 pellicle of pale citron-yellow color. There is also a precipitate of similar particles, but the 

 fluid itself is clear. The organism grows rapidly on sterilized potato, but makes a very 

 slow growth on different nutrient agars and gelatins, such as bouillon-gelatin, Dactylis 

 decoction-gelatin with or without peptone, and Dactylis decoction-agar with peptone. On 

 potato it grew equally well, whether the slices were weakly alkaline or neutral or made 

 slightly acid by the addition of diluted lemon juice. Potato cultures made at a warm sum- 

 mer temperature (probably 20 to 25 C.) often showed a lemon-yellow streak on the second 

 day and in the next days a considerable portion was covered. The cultures were then 

 wrinkled, easily separable from the substratum, and of a deep lemon-yellow color; the 

 margins were coarsely crenate in places. In this condition it reminds one of Bacillus vul- 

 gatus (Fliigge) Migula, and B. mesentericus (Fliigge) Lehm. and Neum., but is distinguish- 

 able from them by its vivid lemon-yellow color. Finally, the bacterial growth covers the 

 whole surface of the potato. Although the colonies are yellow the individual bacteria are 

 colorless. The coloring matter exists in the colonies neither in the form of granules nor 

 crystals. It is not soluble in water or alcohol, and with concentrated sulphuric acid does 

 not give the blue reaction characteristic of lipochrome. 



The organism does not liquefy gelatin. Whether there is any fermentation of sugars 

 or any production of indol has not been determined. It has not been tested for the reduc- 

 tion of nitrates to nitrites or the production of hydrogen sulphide. It is not sensitive to 

 direct sunlight and thrives in sunlight under a Senebier bell-jar filled with a solution of 

 potassium dichromate, as well as under a similar jar filled with ammonium cuproxide. It is 

 not told how these tests were made, i. e., whether plates were poured or fluid cultures used. 

 If only the latter, then the statement is not to be depended upon. 



All the inoculations, both in mature plants and seedlings, failed (methods not given) ; 

 still the number of cases investigated satisfied Rathay beyond a doubt that the bacteria are 

 the primary cause, and it is equally certain he thinks that special unknown conditions are 

 necessary for infection. It is only in the woods, where Dactylis glomerata flowers late, only 

 from the end of May to the beginning of July, and only on the upper leaves, internodes, 

 and inflorescence, that the disease has been observed. Dactylis glomerata is the only grass 

 among several growing in the same place on which this disease appears. 



The disease always makes its first appearance on the surface and only in later stages is 

 the organism found in the intercellular spaces and the fibro- vascular bundles. It has never 

 been found in the cell-contents. It is in the highest degree probable that the bacterium can 

 gain a foothold only so long as floral organs of the plant are enveloped by the leaf-sheath, 

 since no new infections are observed after the inflorescence has emerged. Infection is made 

 possible only by the unexplained disappearance of the cuticle and the drying up of the 

 underlying tissues. 



