Latham: Assimilation of Sterigmatocystis 243 



To explain the reason for the activity of the organism along 

 these lines, there are these suggestions : one, that the fixation of 

 free nitrogen and its excretion in combined form may be a func- 

 tion connected with fructification, since stimulated felts do not 

 produce spores ; another, which is more theoretical and yet more 

 probable, is that the stimulated crop, driven to its most rapid 

 metabolic activity by the stimulant, is forced to consume its carbo- 

 hydrate more economically and therefore finds less energy to use 

 in effecting the combination of the relatively inert and difficultly 

 combinable nitrogen and so must use the more readily assimilable 

 compound nitrogen ; or again, it may be that since by the presence 

 of the stimulant, the fungus can consume carbohydrate more thor- 

 oughly and with less waste, therefore it finds, in what would be a 

 normal amount under ordinary circumstances, a more than neces- 

 sary amount under the favoring influence of the stimulant, which 

 would of course be then potentially a too great supply and the 

 result would be over-feeding in this direction and therefore there 

 would be a tendency to lessened activity in expending energy for 

 nitrogen combination. This last hypothesis is in accord with 

 Moore*s * conclusions on the activity of the root-tubercle bacteria 

 in fixing nitrogen when well supplied with nitrogen compounds, 

 but not in accord with the results of those who find that the fixa- 

 tion of nitrogen is directly proportional to the amount of sugar at 



hand. 



If, however, the absolute numerical results be questioned, there 



can surely be no doubt of the fact that stimulation serves to de- 

 crease the amount of nitrogen to be found in the nutrient sub- 

 stratum, while it has little or no effect upon the relative amount 

 combined in the fungal felt And lastly, if even these results be 

 questioned on the ground that the Sterigmatocystis was not pure 

 but mixed with a nitrogen-combining bacterium — which we con- 

 sider to have been refuted by the evidence of the plate culture 

 before mentioned — there remains still the fact that in the body 

 oi the fungus hyphae in which the normal and stimulated fungi 

 vary so widely in appearance, the relative nitrogen content of the 

 chemical composition remains the same. 



* Moore, G. T. Soil inoculation for legumes. U. S. Dept. Agr. Bur. PI. Ind 

 Bull, 71. 1905- 



