Blight Canker of the Apple Tree. ^21 i 



Gelatin stab. — Growth slow and at first feeble. Beaded or granular 

 along line of needle. Surface growth spreading with irregular or erose 

 margin, which is thick and white, the center thin and granulose ; liqui- 

 faction very slow, becoming evident only after several days, crateriform 

 to stratiform. 



Potato plugs. — Growth feeble, becoming evident after a day or two 

 as a thin moist pearly white coating over the surface of the potato, not 

 viscid. No further change noted even after several days. 



Glucose agar. — ( IVIelted, inoculated, shaken and allowed to cool.) — 

 No gas. Growth in 24 hours vigorous forming a thick white layer at the 

 top, below granular from the minute buried colonies. Little change later 

 except in increased thickness of this white surface layer. 



Milk. — No change until about the third or fourth day when it begins 

 to thicken, becoming very thick by the fifth or sixth day. The milk does 

 not curdle but becomes subgelatinous. Finally after ten days or two 

 weeks the thickened portion gradually settles leaving a clear watery 

 liquid above. At first acitl becoming strongly alkaline. 



Litmus milk. — No change even after two weeks, never thickens. 



Glucose bouillon. — Uniformly clouded at the end of 24 hours with 

 abundant large flocci and frequently a weak pellicle. Little change in 

 growth later. Remaining acid. 



Lactose and saccharose bouillon. — No growth evident even after ten 

 days. 



Three descriptions of Bacillus amylovorus based on cultural char- 

 acters seem to have appeared thus far in literature. The first of these is 

 a part of the classical work on pear blight done by Arthur^ in 1886. He 

 grew the bacteria in various kinds of broths or liquid media and to a 

 limited extent on solid media. The next description to appear was one 

 by Chester (1900) based upon the study of a single pure culture from a 

 blighted pear twig. The organism was grown in but a relatively small 

 number of kinds of media and the reactions recorded differ strikingly 

 from those obtained by Jones i" who published the third and most recent 

 description (T902). The work of Jones was based upon a study of the 

 organism from blighted twigs of both the pear and plum carried in 

 parallel series through many kinds of media and extending over a period 

 of eight months. Numerous successful inoculations were also made with 

 bacteria from these cultures at different times throughout the period 

 during which the cultures were under observation. My own cultural 

 studies while not as extensive as those of Jones tally quite closely with the 

 reactions which he obtained on similar media. It should be recalled in 

 this connection that the bacteria which I had in culture were from the 

 various forms of the disease on the apple tree as well as from the pear. 



