596 BACTERIA IN RELATION TO PLANT DISEASES 



well as some with thin, wrinkled, dull surfaces. Gardner and Kendrick' described and 

 illustrated aberrant colonies of Bad. viridifaciens which appear similar to the rough 

 colonies of BacL phaseoli sojense, and Miss Hedges' described and illustrated a colony 

 of Bad. phaseoli sojense with which Sharp's rough colony appears identical. She states 

 that the convolutions are internal. Smith'' illustrates a colony of Bad. phaseoli which 

 appears rough but which was described as having internal markings. He describes 

 and figures colonies of Bad. malvacearum which are very suggestive of the erosive 

 phenomena described in some animal pathogens. In discussing the peculiar "win- 

 dowed" colonies of this organism he writes: "Occasionally the mottling of surface 

 colonies on agar is so conspicuous as to suggest an intruder .... but inoculation 

 with subcultures produced typical spots on cotton leaves. Moreover, after a few 

 days, such strikingly mottled colonies fill up their thin places." Some of the colonies 

 of Bad. malvacearum appear as rough as the roughest ones of Bad. phaseoli sojense 

 (R). Smith reports and illustrates the development of "liquefaction pits" in colonies 

 of Bad. translnccns \'ar. undidosum. 



Hadley-t has recently reviewed similar or identical observations in the field of gen- 

 eral and medical bacteriology, and has grouped them under the unifying concept of 

 species instability or microbic dissociation. He has attempted to show that physio- 

 logical properties are correlated with such cell and colony changes. Whether the in- 

 terpretation will prove to be correct either in part or in its entirety is immaterial. It 

 introduces a semblance of order into what appears otherwise to be a chaotic mass of 

 isolated observations, and serves as a working hypothesis. In the main, so far as the 

 very meager data of phytobacteriology on this question go, there seems to be a strik- 

 ing parallelism between some of the phenomena reported from the plant and from the 

 animal field. 



BACTERIAL CYCLOGENY 



The controversy which has raged in the other fields of bacteriology relative to 

 cyclogeny of bacteria has hardly been felt in the ranks of the phytopathologists. Un- 

 der special or abnormal conditions, long filaments and chains are produced, and many 

 of the bacterial phytopathogens lose their normal rod shape and become club shaped, 

 Y-shaped, or otherwise branched. Involution or degeneration forms are reported for 

 Bad. tumcfaciens and the legume nodule bacteria in culture and in the galls. Never- 

 theless, the general reaction of phytobacteriologists has been that the protagonists of 

 the cyclogeny concept are dealing with involution and degeneration forms, and that 

 there is no good evidence for believing that bacteria pass through cycles. However, 

 Levine-' has described morphological changes in Bad. tumefaciens. He reports the 

 demonstration of amorphous masses of a jelly-like substance, with occasional deeply 

 stained minute spherical bodies in three-month-old cultures stained with Loeffier's 



' Gardner, M. W., ami Kendrick, J. B.: "Bacterial Spot of Cowpea and Lima Bean," /. Agr. 

 Research, 31, 841-63. 1925. 



^ Hedges, F.: "A Study of Bacterial Pustule of Soy Bean, and a Comparison of Bad. phaseoli 

 sojense Hedges with Bad. phaseoli E.F.S.," ibid., 29, 229-51. 1924. 

 3 Smith, E. F.: Bacterial Diseases of Planls. 



1 Hadley, P.: "Microbic Dissociation," J. Infect. Dis., 40, 1-3 15. 1927. 

 5 Levine, M.: "Morphological Changes in Bacterium tiinufacicns," Science (N.S.), 42, 424. 1925. 



