66 BACTERIA IN RELATION TO PLANT DISEASES. 



also occurs frequent!}' when the flowers, green fruits, or foliage are killed by other 

 causes. In the leaves of ^IniarylUs ataiiiasco the writer obtained red stripes by 

 injecting the A'ellow Bacterium hyacbithi^ but no bacterial disease followed, and the 

 same plant reddens when bruised. Broomcorn shows conspicuous red blotches 

 when attacked by the broomcorn organism, but the parasite itself does not produce 

 a red pigment, while the plant reddens easil}' as the result of aphis-punctures or 

 wounds of an)' sort. Sugar-cane attacked b}' Bacieriitm vascularnni shows a con- 

 spicuous red stain in the bundles, but other causes, such as the gnawings of an insect 

 or the presence of a fungus, may lead to a similar stain, while the bacterium itself 

 does not produce any red pigment. 



CRYSTALS. 



Determine the nature of the crystals obser\'ed in the various media. Many of 

 these are double ammonium salts ; others result from the action of trypsin on pro- 

 teids. Cr)'sta]s which are not due to the drj'ing out of the media are common 



phenomena in old cultures of many sorts, especially if 

 the media were not originally saturated with alkali 

 (soda or potash). Fig. 57 shows two types of crj'stals 

 formed in +15 nutrient agar b)' two green-fluores- 

 cent organisms recei\'ed from\'an Hall as Psciidomonas 

 syringcr^ and a third type produced by the olive 



"s'' \ , "'\^ tubercle organism. 



/ V <^ 



QUESTION OF EXISTENCE OF ENZYMES. 



h ^ *o J ■**« '^\\<t enzymes of English writers are the diastases 



»" ^ i of Duclaux. They are chemical substances, the exact 



e composition of which has not been determined. They 



Fig. 57.* may be regarded as the working tools of protoplasm. 



The following are some of the best known kinds : 



(I.) Diastasic (starch-destroying). (5.) Lab or rennet (casein-forming). 



(2.) Inverting (sngar-splitting). (6.) Lipase (fat-splitting). 



(3 ) Cyloliydrolytic (cellulose-dissolving.) (7.) Pectic (pectin-splitting). 



(4.) Proteolytic (peptonizing). (8.) Oxidases (oxidizing). 



Trypsin is common. Pepsin is not known to be produced by bacteria and 

 should be searched for. 



Many bacteria invert cane-sugar, but invertase is believed to be rare. This, 

 however, may be an ill-founded conclusion. The experiments of various animal 

 physiologists have shown that when cane-sugar is injected into the blood-stream it 

 is excreted unchanged, and according to Julius Sachs cane-sugar, inulin, etc., must 



''Fig. 57. — Crystals formed in cultures of Baclcnuiu syriiigac (van Hall), i. From tube 11, 

 Aug, 14 (agar stock 693), from \'aii Mall's II, /..-., his own isolation corresponding to a, fig. 56. 

 2. From tube I, Aug. 14 (stock (.93), from van Hall's I, which is from Beyerinck's old isolation (sec 

 b, fig. 56) X 3- Nos. I and 2 drawn /Vug. 30, 1902. 3. Crystals formed on slant litmus-lactose agar 

 which was inoculated with the organism causing olive-knot. Al)0ut one-half inch of slant in middle 

 part of culture i month old, i. i., made January 20, 1904; drawn February 17-19. X 3. Tempera- 

 ture during growth, 20° to 25° C. 



