ISS ROYAL SOCIETY OF CANADA 



Xo nodules were found on the roots of Ginuiocladiis, Glcditschia 

 or Cercis canadensis belonging to the sub-order Caesalpineae, but mvcor- 

 hiza were present in all cases. 



2. The following is a list of Papilionaceae from which Ps. radicicola 

 has been isolated: — 



Trifolieae, — Medicago sativa, Jilclilotus alba, TrifoUum incarna- 

 fiivi, T. pratense, T. repens. 



Hedysareae, — Desmodiiim acuminatum, D. canescens, D. nudi- 

 fionim. 



Vicieae, — Ticiu villosa, Lailiyrus sativus, Pisum sativum. 



Phaseoleae, — GJycina hispida, Apios tuberosa, Pliaseolus vulgaris. 



3. Media. — Media are required for the bacteria and for the 

 leguminous plants. It is desirable that these be common media, that 

 is, serving at once for the growtb of the leguminous host and the bac- 

 terial parasite. These media should be nitrogen free or nitrogen poor 

 so as to introduce and compel the iixation of atmospheric nitrogen. 

 In other words, they should be such as best to introduce the specific 

 functional activity. It is well also in preparing media that the mater- 

 ials be few and easily available, and the processes be simple and rapid. 

 The media used in these experiments meet these requirements and offer 

 additional advantages. 



Green plants and bacteria contain and require for their growth 

 certain elements, and most of these elements are present in due propor- 

 tion in the ashes of burned plants. For example, wood ashes contain 

 phosphates, sulphides and chlorides of potash, soda, lime, magnesium 

 and iron. Wood ashes contain no nitrogen. ^Yater and air may be 

 had free from combined nitrogen and they furnish the rest of the 

 essential elements — oxygen, hydrogen and free nitrogen. Green plants 

 get their energ}' for growth from the sunshine and the nitrogen fixing 

 bacteria get their energy for growth indirectly from sunshine, wlien 

 they are living within their host. ^Mien living independent of their 

 host, a source of energy growth must be supplied the bacteria. Sugar 

 affords such a force of energy and is free from nitrogen. Some of 

 these relations are indicated in the table below. 



Essentials for Growtli. 



Green plant alone. Bacteria alone. In association. 

 Wood ashes. TYood ashes. "Wood ashes. 



Water. Water. Water. 



Air. Air. Air. 



Combined X. Sugar. Sunshine. 



Sunshine. 



