NEGATIVE EVIDENCE. 85 



the nectaries of very many flowers from differ- 

 ent places under all the possible circumstances 

 in which nectar might be secreted, did he feel 

 justified in saying, "We may therefore safely 

 conclude that the nectaries of the above named 

 orchids neither in this country nor in Germany 

 ever contain nectar." Even then he restricted 

 the negative conclusion to the two countries 

 in which the exhaustive examinations had been 

 made. 



But he did not rest with this negative evi- 

 dence. It was strong enough to convince him 

 that there was no ordinary nectar, but the 

 further evidence that he presents shows how 

 quickly negative evidence falls into the back- 

 ground in the presence of even the most indirect 

 positive evidence. He was thoroughly con- 

 vinced that these orchids require the visits of 

 insects for fertilization, that insects visit flowers 

 for the attractions offered in the way of nec- 

 tar, pollen, etc. ; that nature could not deceive 

 insects by a permanent imposture, and yet that 

 in these orchids the ordinary attraction was 

 absent. It was as if a crime had been com- 

 mitted, and he were asked to believe there was 

 no criminal. 



In examining the nectaries of the several 

 species of orchids he was "surprised at the 



