BIOLOGIC FORMS 



151 



between the biologic forms of the fungus and certain of their 

 host-plants become complicated by the existence of biologic 

 forms of the host-plant. Such a case is illustrated diagram- 

 matically at fig. 44. Here we have shown the results of 

 experiments in which B. mollis and a plant called B. 

 ' hordeaceus ' were inoculated with conidia of the forms of 



FIG. 44. In this diagram, and in tlie following one, the number of 

 inoculations made and the results obtained are expressed in the form of 

 a fraction, in which the numerator indicates the number of times in which 

 infection resulted, and the denominator the number of leaves inoculated. 



the fungus growing on B. arduennensis, B. commutatus, B. 

 secalinus, and B. adoensis. In every case B. ( hordeaceus ' 

 proved susceptible, while B. mollis remained immune. 

 Nevertheless, B. ' hordeaceus ' proved on close examination 



