species varying very slightly would require difficult bacili. One- 

 investigator who was working at this particular subject, has indeed 

 succeeded in showing that in many cases a particular leguminous 

 plant thrives much better when it is supplied with its particular 

 bacilli than when it is supplied with the bacilli of another species. 

 Thus three robinia plants were grown simultaneously ; No. 1 was 

 not allowed any bacilli at all, No. 2 was allowed the bacilli from 

 pea-tubercules, and No. 3 the bacilli from robinia, and as a conse- 

 quence Nos. 1 and 2 in S^ months were mere bare stalks. No. 3' 

 was a fine well grown plant. Three pea-plants were treated in the 

 same way; No. i was supplied with the bacilli from pe i-tubercules, 

 No. 2 with bacilli from lupin, and No. 8 with bacilli from robinia. 

 In about eight weeks No. 1 was a thriviug plant. No. 3 a poor 

 withered up specimen, and No. 2 rather intermediate. But I don't 

 think this proves that even these three are distinct species of bacilli. 

 Klein has worked at the nodules in the lupin and has found that the 

 bacilli are of two kinds, one about twice as numerous as any other. 

 He says "the examination of the nodules was carried out towards 

 the end of last year ; the nodules were very abundant on the roots 

 obtained ; some were of a round shape, others oval, some were fiat, 

 others more of spheroidal shape ; all were more or less eccentrically 

 attached to the roots, in fact, as is well known, were local eccentric 

 thickenings of the roots themselves. A transverse section through 

 a root nodule, shews underneath the brown covering a yellowish 

 brownish mass representing the main cellular tissue of the nodular 

 excrescence, and gradually passing into the cellular and vascular 

 tissues which form the central or axial portion of the root itself." 

 *• Examined under a microscope; the yellowish substance is seen to- 

 contain large numbers of cylindrical bacilli witli ronn<!ed ends, and 

 amongst these some which are short oval, and others which are 

 dumb-bells of spherical or short oval corpuscles, but the cylindrical 

 bacilli are barely predominating in numbers " The bacilli are 

 small and rather difhcult to see. I saw one or two preparations of 

 them in tbe Bacteriological Department at the meeting of the 

 British Medical Association held at Bristol in the beginning of last 

 August. They seemed rather smaller than tlie bacillus of " tuber- 

 culosis " and very difficult to observe in a section of the nodule. 

 They are also very slow in staining. The course of proceedings in 

 the formation of the nodule is as follows : — A bacillus at some stage 

 of its life penetrates the point of one of the minute hairs of the root 

 of the plant, and spreads by going through the whole length of the- 

 hair into the root itself ; its presence there causes the exuberant 

 growth of cells which constitute the nodule, whilst colonies of the 

 bacillis grow in its deeper parts, surrounded by some layers of these 

 cells. The bacilli apparently benefit by the jucies of the plant, 

 whilst the plant benefits by the nitrogen, which in some way, it is- 



