140 CROWN-GALL OF PLANTS. 



CTJLTiniAL CHARACTERS. 

 EXPLANATORY STATEMENT. 



Such comparative studies as we have been able to make are included 

 in the following tables and memoranda. Many of them were made or 

 repeated in the spring and summer of 1910 during the preparation of 

 this bulletin. 



In offering these incomplete data it may be pointed out that prob- 

 ably some errors have slipped into these records, as the time was not 

 sufficient for exhaustive tests of all the cultural characteristics of 

 all these strains and for the elimination of all possible intruders 

 through repeated poured plate separations and further inoculations. 

 It is the more likely that some errors are included owing to the fact 

 that in 1910 a number of our forms had ceased to be pathogenic, e. g., 

 peach, chestnut, apple, quince; but whether this was due only to loss 

 of a peculiar quality, or to the right organisms having been driven 

 out of our cultures by unobserved intruders was not determined 

 beyond all doubt, except that clearly the "old apple" appeared to be 

 something entirely different from what we had on the start, and very 

 probably the quince and the sugar beet. 



To straighten out fully all the tangle of interrelations here touched 

 upon would require so many additional months of work that it has 

 appeared best to publish at once what we have, leaving the unsettled 

 problems for further study. 



GROWTH ON AGAR. 



When these organisms were grown for 3 days at 23° to 25° C. upon 

 slant +15 peptonized beef agar containing 1 per cent agar flour, and 

 inoculated by needle stroke from 18-day-old slant agar cultures, there 

 was in each case a well-developed shining white streak and some 

 growth in the condensation water. The agar was not stained. Slight 

 differences not easily definable were visible, the most pronounced of 

 which were the following : 



(1) White watery translucent streaks: Newest daisy, arbutus, new 

 apple, apple hairy root, new chestnut, grape, alfalfa (the last 

 showing transitions to 2). There were no crystals, or only a trace 

 (new apple). 



(2) Similar streaks but whiter, i. e., less translucent: Old daisy, 

 peach, hop, old rose, new rose, beet, cotton. Numerous prismatic 

 crystals, except in beet which had only a few. 



(3) White shining flat growth, i. e., thinner than in the preceding 

 and trace of crystals: Old apple. The growth of this when first 

 isolated (2 years ago) was like No. 1, i. e., translucent watery. (See 

 under Morphology, p. 129.) 



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