692 



SCIENCE. 



LN. S. Vol. YIII. No. 203. 



slowly in cornstarch cooked in water, and 

 sugar was not formed. Both change cellu- 

 lose to sugar and the non-parasitic one gives 

 a slow fermentation when the cellulose is 

 made up with peptone. In pure moistened 

 cellulose the growth of both was very slow 

 and sugar was not formed in either case. 

 Both prefer high temperatures. It differs 

 from the pear blight germ in the following 

 ways : Feeble growth in healthy tissues 

 and no sj'mptoms of blight (young twigs and 

 unripe fruits of the pear and quince). In 

 unripe fruits it was alive at the end of ten 

 days and in some cases had extended to the 

 opposite side of the fruit and into the seeds. 

 Mixed in water in equal parts with the pear 

 blight germ and inoculated into twigs, blight 

 ensued, but when the tissues were examined, 

 at the end of ten days, only B. amylovorus 

 was found, although several attempts were 

 made to isolate the other germ. 



Unlike pear blight, it ferments potato 

 broth, pear broth and cane-sugar solution, 

 with a copious evolution of gas. A large 

 fermentation tube of Smith's solution 

 yielded about 200 cc. of gas in 10 days. 

 This consisted of 6.2% nitrogen, 61% car- 

 bon dioxide and 32.8% hydrogen. The 

 growth in broth made by cooking unripe 

 pears in water was slower than that of B. 

 amylovorus and in 48 hours the fluid became 

 a deep green. In peach broth made in the 

 same way the same deep green color ap- 

 peared and zoogloete were quite abundant. 

 The writer has not been able to discover 

 zoogloese in cultures of the true blight 

 bacillus. In potato broth this germ grew 

 much more rapidly than B. amylovorus and 

 gas production began in a few hours. 



This organism is best obtained by placing 

 pieces of tissue in bouillon. The same or 

 a similar germ was also obtained by washing 

 the surface of healthy twigs into bouillon 

 or Smith's solution. One which turned 

 pear broth green was also obtained from 

 the surface of grains, especially wheat. By 



means of platinum needle transfers from 

 the interior of freshly blighted twigs the 

 true bacillus of the blight may be separated 

 with less danger of contamination. The 

 fact that this germ does not apparently 

 injure the trees when inoculated into them, 

 also that it is obtained by washing the sur- 

 face of healthj;^ twigs, proves that it has no 

 essential connection with the disease, and 

 renders it probable that it is a surface 

 germ. This work was carried on in the 

 laboratory of Dr. J. C. Arthur, at Purdue 

 University. 



lAJe History and Characteristics of the Pear- 

 Blight Bacillus. Mebton B. Waite. 

 Beginning in the spring, the germs on the 

 new growth first appear on the nectar disks 

 of the blossoms. The bacilli live and mul- 

 tiply in the nectar and are able to enter the 

 nectar glands without a puncture or injury, 

 and thus normally get inside their host. 

 The distribution from flower to flower and 

 tree to tree is through the agency of insects, 

 mainly flower- visiting sorts. Infection also 

 occurs on the j'oung shoots, and less fre- 

 quently on the fleshy bark through injuries. 

 Insects and birds are agents of distribution 

 and inoculation in these cases. No evidence 

 has been found that the germs are carried 

 by the wind. The organism usually dies 

 out in the twigs which are blighted and 

 dead, but in certain cases the germs manage 

 to keep alive during the summer by making 

 slow progress in the fleshj' living bark. Such 

 cases may succeed in living over winter. 

 Winter weather is favorable to the longevity 

 of the organism, on account of the mois- 

 ture and low temperature. These cases of 

 ' hold over blight ' start off again in spring 

 and exude quantities of gummy matter full 

 of the bacilli. This is visited by insects, 

 especially flies and wasps, and is carried on- 

 to the newly opened flowers, thus complet- 

 ing the cycle of the year. In brief, the 

 characters of the germ are as follows : An 



