95 



As a matter of fact, the just-mentioned treatise is one of BEIJE- 

 RINCK'S masterpieces, not only because of its clear argumentation and 

 the thoroughness with which the morphological as well as the anatom- 

 ical characteristics of the nodules and their bacteria are described, but 

 also because of the simplicity of the technique applied in the isolation 

 of the bacteria, and of the originality of the methods of studying the 

 physiology of these bacteria. In this first treatise of BEIJERINCK in 

 the domain of "general microbiology" one finds the basis of the appli- 

 cation of "auxanography", and use is made of luminous bacteria as 

 reagents for enzymes. 



The bacteriological side of BEIJERINCK'S investigation has been 

 surveyed in Part III of this book. Here, however, a few points of 

 botanical interest must be made plain, about which BEIJERINCK has 

 quite often been completely misunderstood. 



Already in his 1888 treatise BEIJERINCK stated that he had not 

 succeeded in obtaining nitrogen-fixation with cultures of Bacillus 

 radicicola (in the beginning he wrote the species name with a capital r) 

 which he had isolated. His opinion on the significance of these nodules 

 was really completely different from what one usually supposes. He 

 suggested that the bacteria produce protein from matter conveyed by 

 the plant itself; the bacteroids were to be considered as the reservoirs 

 for this protein, which, in a later stage, would be used by the plant. As 

 an advantage, for the bacteria, of this symbiosis, he indicates that 

 when the nodules decay there occurs a great increase in the number of 

 bacteria, at the expense of the deceased cell tissue. The latter opinion, 

 however, he withdrew in later years. 



It seems doubtful whether BEIJERINCK, when writing his treatise, 

 was already acquainted with the extensive report on the experiments 

 of HELLRIEGEL and his co-worker H. WILFARTH, in which nitrogen- 

 fixation by Leguminous plants under natural conditions was con- 

 vincingly proved. It is certain, however, that BEIJERINCK in 1892 

 visited HELLRIEGEL in Bernburg, where the latter was experimenting 

 with pure cultures sent to him by BEIJERINCK. 



Most botanists and agriculturists will be interested to know BEIJE- 

 RINCK'S view on HELLRIEGEL'S experiments. This vie\v was long 

 known to the writer from oral conversations, but BEIJERINCK appears 

 to have hesitated to make it public. His viewpoint has not been ex- 

 pressed, for instance, in the few very short communications of BEIJE- 

 RINCK on the nodules on the roots of t\\ePapilionaceae'm 1890 1 ) and 

 1894 2 ), (interesting observations on these leguminous nodules are also 

 to be found in his lecture before the "Hollandsche Maatschappij der 



J) Kunstliche Infection von Vicia Faba mit Bacillus radicicola, Ernahrungsbe- 

 dingungen dieser Bacterie, Botanische Zeitung 48, 837-843, 1890 (Verzamelde Ge- 

 schnften 2, 321-326). 



2 ) Uber die Natur der Faclen der Papilionaceenknollchen, Centralblatt fur Bak- 

 teriologie und Parasitenkunde 15, 728-732, 1894 (Veyzamelde Geschriften 3, 49-53). 



