194 THE METHOD OF DARWIN. 



indicate nothing at all. Had his conclusion 

 been left at this point, it would probably have 

 been accepted as both interesting and quite cer- 

 tain. The degree of certitude with which such 

 an inference is received depends on the number 

 of facts involved, their relation to each other, 

 and the degree to which they act as convergent 

 evidence toward the one conclusion. In these 

 respects the facts were all that could be desired. 

 It would seem that, if it is possible to make any 

 inferences at all concerning function from the 

 structure of plants, it would have been so in this 

 case. 



For Darwin, as for every true student of 

 nature, deductions exist only to be verified. 

 The indirect evidence from structure he supple- 

 mented by experiments on the actual produc- 

 tion of seed by the two forms. He might have 

 pointed with pride to the cowslip as a plant in 

 an actual state of transition, as a fine illus- 

 tration of his theory. But after describing in 

 detail the differences of structure in the two 

 forms of flower in the cowslip, he said, "The 

 question seems well worthy of careful investi- 

 gation." He made preliminary experiments 

 which of themselves would have been conclu- 

 sive, but used them to lay a basis for his much 

 more extensive experiments; they suggested 



