35o FIXATION OF FREE NITROGEN BY BACTERIA. 



greater part is composed of albumin. Certain enclosures are also 

 frequently observed, A. B. FRANK (VII.), for instance, having 

 noticed such bodies in the bacteroids of individual nodules of peas. 

 He regarded them as amylodextrin, the discovery leading him to 

 the opinion that two kinds of nodules develop on these Papilio- 

 nacece : albumin nodules and amylodextrin nodules. A subsequent 

 investigation of this matter by H. MOLLER (I.) showed, however, 

 that these doubtful enclosures do not consist of carbohydrates, but 

 of waxy or fatty substances ; that they are also to be found in the 

 bacteroids of the " albumin nodules;" and that, moreover, there 

 is but little probability of the existence of dimorphism in the 

 root-nodules of the pea, since these enclosures are also occasionally 

 met with in the bacteroids of the nodules of other Leguminosce 

 (e.g. Trifolium repens). 



Concurrently with the reproduction and transformation of the 

 bacteria marches the development of the nodule, which not only 

 increases in size, but also becomes richer in nitrogenous compounds. 

 This gradual increase in the percentage of combined nitrogen in 

 the nodules and the relative proportion of this substance there 

 present, as compared with other parts of the root, were quanti- 

 tatively investigated by J. STOKLASA (II.). From his results a 

 few figures have been collected into the subjoined tables, which 

 refer to yellow lupins : 



That this nitrogen of the nodules was chiefly in the form of 

 albumin is revealed by the following table: 



The figures just given are surpassed in two analyses made by 

 A. B. Frank, according to which, a few of the pea nodules examined 

 by him contained 6.94 per cent., and those from the dwarf bean 

 7.44 per cent, of nitrogen, corresponding on the basis of the 

 factor 6.25 to an albumin content of 43.4 and 46.5 per cent. As 



