32 TKANSACTIOXS AND PKOCEEDIXGS OF THE [Sess. LXi. 



sterilised a scalpel by heating in a flame, cut the nodule. 

 Dip a platinum needle into the cut surface, and streak the 

 gelatine already prepared. It is well to have a large 

 surface of gelatine, as the Bacillus radicicola is an aerobic 

 form. It is important to remember that this bacillus will 

 not grow on the ordinary gelatine, but there must be 

 incorporated with the gelatine-nourishing medium a 

 decoction of leguminous shoots or leaves. Having ob- 

 tained in this way, after a few days, a pure growth of 

 the bacillus, in order to inoculate plants growing in 

 pots some of the bacilli are transferred to water, a little 

 of which may be sprinkled over the soil in which the 

 plants are growing ;" or, better still, by means of a glass 

 tube the mixture is introduced to the deeper layers, near 

 the roots. The experiments of Nobbe and Hilltner aimed 

 at winning information and clearness in three directions^ 

 viz.: (1) What are the true factors and occurrences by 

 which a nodule-beset leguminous plant is able to make use 

 of the free nitrogen ? (2) What is the action and efficacy 

 of the nodules in soils holding different quantities of 

 nitrogen ? (3) Are the bacteria from the warts of the 

 different leguminous species one and the same species of 

 bacterium, or has each leguminous group or species its own 

 distinct nodule-former ? 



As to (^)uestion 1. — Some hold that the nitrogen assimi- 

 lation is by means of the green leaves, others that the 

 bacteria are the chief agents in taking up the free nitrogen. 

 Nobbe and Hilltner believe strongly tliat the power is 

 vested in the bacteroids, which, arranged in the form of a 

 network, expose a large surface to the air, to which the 

 bacteroids come into relation as regards nitrogen in the 

 same way as the gills of a fish to oxygen. The conclusions 

 from their experiments so far are : (a) Nodules whose 

 bacteria have not followed on to the bacteroid stage (as 

 happens in certain circumstances) are of no value to the 

 plant, the bacteria in them being out-and-out parasites, 

 and performing no nitrogen assimilation, (h) The stronger 

 in life tlie bacteria are, the less is the tendency to become 

 bacteroids ; the stronger the nodule-possessing plants, the 

 easier is tlie changing from bacteria to bacteroids. (c) 

 With bacteroid formation comes nitrogen assimilation. 



