WILT OP CUCURBITS. 



2 8 7 



thinner, according to age, culture-medium, and kind of stain used. , Flagella-stains in par- 

 ticular, affect an outer part not stained by ordinary methods (figs. 83 and 84) . The organism 

 has a distinct capsular portion, the solution of which appears to give rise to the viscidity. 

 This viscidity occurs during active growth, and may continue for some time. When taken 

 directly from the plant (fig. 52) this bacillus is usually viscid but not always. Often with 

 care the slime may be stretched out to the distance of 20 to 40 cm. (once 76 cm.). The 

 resulting cobwebby threads generally yield pure cultures of this organism and when stained 

 on a slide and examined under a microscope are seen to be made up of bacilli embedded in a 

 tenuous slime which separates them by considerable intervals (Vol. I, figs, 13 and 14). The 



Fig. 81.* 



organism is also sticky, at least in some of the stages of its growth, on agar, gelatin, potato, 

 carrot, sweet potato, coconut-flesh and various other solid culture-media. In one instance 

 the slime from a potato-culture was drawn out 53 cm. before it gave way. On potato, up 

 to the sixth day and sometimes longer, the organism is actively motile, even when examined 

 from very viscid cultures. Potato cultures 10 to 1 8 days old are usually as sticky as younger 

 ones. This slime does not dissolve readily in water and hence failure may occur in making 

 poured plates. Cultures in potato-broth and in sugared fluids finally become ropy, and 

 then most of the individuals or all of them are dead. 



*Fio. 81. Cross-section of one bundle of fig. 80. At bottom and left-hand side are numerous intercellular spaces 

 occupied by bacteria. The bundle has been hollowed into a cavity, and at x, and y parenchyma cells are also occupied 

 by the bacteria. These can be followed through a whole series of sections, but the method of entrance into these cells 

 has not been made out clearly. Fixed in Carnoy 48 hours. Drawn with a Zeiss 16 mm. apochromatic and No. 12 

 compensating ocular. Slide 354-2, middle section, middle row. 



