S. G. Paine and W. F. Bkwlky 201 



Aplanohacter michiganense make it at least probable that the two 

 organisms are identical. But whereas Smith claims to have made 

 repeated successful inoculations with his organism and has stated that 

 virulence is retained for some months in artificial cultures the organism 

 here described has not shown any sign of parasitism, although repeated 

 attempts at infection have been made, the earliest being within 10 days 

 of its isolation from the plant. 



Three possibilities then arise. Firstly, the strong similarity between 

 A. michiganense and the organism here described may be purely super- 

 ficial and illusory. Secondly, the two diseases may have been superposed 

 in the case of the striped plants from which the organism was obtained, 

 the method of cultivation adopted by the authors having destroyed the 

 virulence of the parasite so that infection was not obtained. Thirdly, 

 the two organisms are actually identical, the organism being really a 

 saprophyte and growing so strongly in the dead tissue and in artificial 

 culture as to mask the presence of the true parasite. The authors put 

 forward the third suggestion with great hesitation in view of the wide 

 experience of Dr Smith and of the obvious care exhibited in all his work. 

 In this case, however, many of his recorded inoculations seem to have 

 been made by an assistant, and with material derived by crushing dis- 

 eased tissue. Again, the very viscid nature of the growth of the organism 

 in artificial culture would tend to make one suspicious of the purity of 

 colonies appearing on a plate since such a slime might well conceal a 

 second organism, especially such a one as Bacillus lathyri, whose size 

 and shape are so closely similar to those of Aplanohacter michiganense. 

 The authors are emboldened to put forward this view by the statement 

 of Smith that "when this organism was first discovered the writer 

 thought he observed motility." 



Supposing that Aplanohacter michiganense were proved to be a 

 saprophyte the question w^ould arise as to the possible identity of 

 "Stripe Disease" with the "Grand Rapids Disease." On the face of it 

 such a possibility seems to be a remote one. In Smith's account of his 

 disease no mention is made of any external markings either on the stem 

 or the fruit. These are such a very distinct feature of "Stripe" that 

 they could not possibly have been overlooked. The morbid anatomy in 

 the two cases is however identical; the photograph which appears in 

 Smith's work (8), Fig. 72, p. 163, might well have been taken from a 

 section of a "striped" plant. The lesions in the pith and the presence of 

 bacteria which appear in the outer layers of the cortex are quite char- 

 acteristic of "Stripe" disease. 



Ann. BioJ. vi 14 



