Pethybridge and Mtirphy — Bacterial Disease oj the Potato. 23 



V. Description of the Organism. 



A. Morphological Characters. 



(1) Form and Arrangement. — The organism when examined in hanging 

 drop prepared from a young agar-slant culture is rod-shaped, occurring very 

 frequently in pairs, sometimes in threes, and not infrequently in long chains. 

 In stained preparations, made direct from diseased tissues, these long chains 

 were not observed. 



(2) Size. — In breadth it varies but little, being usually about 0'9 u broad. 

 The length, however, is very variable. Single individuals range from 1'3 jj, to 

 1"8 fi ; pairs are found up to 2'5 ju ; and the long chains measure from 20 ju to 

 70 fi in length. The individuals composing the long chains are usually them- 

 selves very long ; the first three members of one siich chain, for example, 

 measured 8-2 ju, 9'3/i, and 7 "4/* respectively. When taken direct from diseased 

 tissues, the organism is found on the whole to be slightly smaller, being about 

 0'7(U broad, and from 0'9 /^ to l^/c* long. All measurements were made on 

 fixed and stained preparations. 



(3) Motility and Flagella. — The organism, whether obtained direct from 

 diseased tissues or from artificial cultures, exhibits very active movements of 

 a rapid swimming or " darting " kind. Some little difficulty was at first 

 experienced in satisfactorily demonstrating the presence, number, and mode of 

 attachment of the flagella. Trials with Bunge's and Peppler's mordants, 

 followed by staining with carbol-fuchsin, gave unsatisfactory results. By 

 following closely, however, the details of the method given by Ellis (13), using 

 Loffler's " Fuchsin-Tinte " (freshly prepared) as a mordant, followed by an 

 alcoholic solution of fuchsin as a stain, good results were obtained. The 

 number of flagella found varied from one to five; and the arrangement was 

 found to be peritrichous. 



(4) Staining. — No time was expended in comparative trials with different 

 stains, it being found that carbol-fuchsin gave satisfactory results. Gram's 

 method produced a negative result both in young and in old cultures. 



(5) Spores. — Spores were not observed in any of the cultures, and, as pre- 

 viously stated, an attempt to obtain the organism fi'om affected stalks, which 

 had been hanging since the previous summer in the laboratory, failed. 



B. Cultural Characters. 



(6) Gelatine Plates. — The colonies appear to the naked eye when plated out 

 in potato-gelatine on the second day at laboratory temperature as minute 

 whitish dots with no appearance of liquefaction if submerged, but somewhat 

 shiny and with slight indications of liquefaction if on the surface. After the 



