THE NODULE BACTERIA. 345 



followed immediately by their general recognition in scientific 

 circles. For example, H. DE VRIES (II.) in 1877 looked upon 

 them as non-essential. Moreover, when J. BRUNCHORST (I.), in 

 1885, examined them more closely, he came to quite a different 

 conclusion, and defined the supposed bacteria as organised albu- 

 minoids collected in the interior of the nodule cells, and therefore 

 termed them bacteroids (on account of their external resemblance 

 to bacteria). Hence the term bacteroidal tissue, applied to the 

 internal portion of the nodules in which these organisms appear in 

 large numbers. Remarkably enough, Brunchorst's opinion found 

 favour in the eyes of A. B. FRANK (V.), although conflicting with 

 his own discoveries made in 1879. ^- TSCHIRCH (I.) also ranged 

 himself on the side of Brunchorst. 



A complete revolution of opinion took place in 1888, when 

 BEYERINCK (XIV.) indubitably established the fungoid nature 

 of these supposed pseudo-bacteria, by isolating them from the 

 nodules, and cultivating them further in artificial media. The 

 pure culture obtained from the individual species of Papilionacece 

 exhibited certain slight but undeniable differences, which, however, 

 were not so extensive as to make their discoverer feel justified in 

 classifying the organisms as separate species, so he defined them 

 as varieties of a single species, for which he proposed the name of 

 Bacillus radicicola. The artificial formation of nodules induced 

 by inoculating the roots of Leguminosae with such pure cultures 

 was successfully attempted a year later by Prazmowski, and will 

 be noticed in 195. The bacillus in question develops either 

 feebly or not at all on ordinary nutrient gelatin, this substratum 

 being too rich in nutrient materials. Beyerinck recommends a 

 decoction of the leaves of Papilionacece, with the addition of 7 per 

 cent, of gelatin, J per cent, of asparagin, and J per cent, of cane- 

 sugar. The requisite degree of acidity in the medium is repre- 

 sented by about 0.6 c.c. of normal acid per 100 c.c. The plates 

 coated with this nutrient medium are inoculated with an infusion 

 prepared by mixing a few c.c. of sterilised water with a small 

 portion of the contents of the bacteroidal tissue of a fresh, young 

 nodule that has been previously washed with water, then steeped 

 a short time in alcohol, freed from the latter by means of ether, 

 and finally cut open with a sterilised knife. The small quantity 

 of inoculating liquid will be absorbed by the gelatin, leaving the 

 bacteria on the surface, where their growth progresses in the 

 most favourable manner. Here they develop to small mucinous 

 colonies that do not liquefy the gelatin. 



Two forms of cells will be immediately noticeable in prepara- 

 tions made from such a culture. Beyerinck distinguishes them 

 as rods and rovers. The former have a breadth of i /z and a length 

 of 4 to 5 ju, and wander eagerly towards the edge of the cover- 

 glass, where fresh oxygen obtains access. As veritable dwarfs in 

 comparison with these are the rovers, which are only 0.9 p long 



