Makcii 31, 1905.] 



SCIENCE. 



503 



spots on several different occasions yielded 

 bacteria in enormous numbers, of one kind 

 and in practically pure culture. Very 

 characteristic also was the appearance on 

 the under surface of the spots (the season 

 was wet) of red crusts or scabs. These 

 were so numerous as to be quite conspicu- 

 ous. They consisted of bacteria which had 

 oozed from the interior of the spots. 



The infection takes place by way of the 

 stomata and is favored by i-ainfall or dew- 

 fall. No insect injuries are necessary. 

 The disease was obtained in the hot-house 

 under strict control conditions by dissolving 

 pure slant-ag'ar eulluies of the organism in 

 sterile Avater and atomizing this upon the 

 plants. Spots were visible at the end of 

 ten days and Avere well developed in five or 

 six weeks. Such spots contained the char- 

 acteristic bacterial focus and yielded, on 

 making poured plates, enormous quantities 

 of the organism used, and in most cases 

 nothing else. The disease was likewise pro- 

 duced in broom corn, starting with bac- 

 terial colonies obtained from leaf spots on 

 field sorghum. 



The red stain is a host reaction. The 

 organism is not red, nor yellow, but pure 

 white. It is not a yeast and is not asso- 

 ciated with yeasts or with fungi. It does 

 not produce gas but is strictly aerobic in 

 peptone water Avith varic us carbon foods 

 (dextrose, saccharose, lactose, maltose, 

 mannit and glycerine). It forms small, 

 round, Avhite, slow-growing shiny surface 

 colonies on agar plates. The groAvth on 

 agar is often sticky and hard to remove; 

 the organism blues litmus milk decidedly, 

 and finally renders it gelatinous; it does 

 not liquefy gelatin, does not reduce ni- 

 trates, produces little if any indol, grows 

 very slowly on moist silicate jelly made 

 Avith Fermi's solution, has little diastasic 

 action on potato starch jelly. On potato 

 cylinders growth. is white and much the 

 color of the potato ; grays the potato moder- 



ately; clouds bouillon moderately. In 

 bouillon there is a thin white rim, and in 

 old cultures often zoogkefv and sometimes 

 a thin pellicle breaking doAvn easily. Slow, 

 long-continued growth in Uschinsky's solu- 

 tion, not much precipitate. Resisted dry- 

 ing 96 hours. GroAvs not at all or very 

 feebly at 37.5° C. ; grows more rapidly at 

 30° than at 20° C. ; minimum temperature 

 about 6° C. Thermal death point 47° C. 

 Stands freezing Avell, i. e., only about 20 

 per cent, killed. Occurs in the host plant 

 and in culture media as a short rod with 

 rounded ends, single or in pairs or rarely 

 fours. It is motile but non-sporiferous, 

 so far as yet observed. 



Some varieties are much more subject to 

 the disease than others, and there is good 

 hope of overcoming the disease by selecting 

 resistant plants for propagation. 



Fecan Scab {Fusicladium effusum Wint.) : 

 Mr. W. A. Orton, Department of Agri- 

 culture. 



This paper Avill be published later as a 

 bulletin of the Bureau of Plant Industry, 

 U. S. Department of Agriculture. It de- 

 scribes a disease of considerable economic 

 importance, caused by the above-named 

 fungus, AA'hich attacks the leaves, tAvigs and 

 nuts of cultivated pecans in our southern 

 states. The fungus occurs on either side 

 of the leaves and on the petioles, producing 

 dead spots or distortions and defoliation. 

 The new groAvth of the tAvigs is sometimes 

 killed, but the greatest injury is to the 

 nuts. The microscopic and cultural char- 

 acters of the fungus Avere described. 

 Fusicladiiim caryigeinim E. & L. was 

 found to be the same species. Favorable 

 results from spraying experiments were re- 

 ported. 



Factors which Determine the Spread of 

 Pear Blight: Mr. M. B. Waite, Depart- 

 ment of Agrieultiire. 



