84 THE METHOD OF DARWIN. 



" I have looked to all our common British 

 species and could find no trace of nectar; I 

 examined, for instance, eleven flowers of O. 

 maculata, taken from different plants growing 

 in different districts, and taken from the most 

 favorable position on the spike, and could not 

 find under the microscope the smallest bead of 

 nectar." Sprengel believed that these plants 

 exhibit an organized system of deception, "for 

 he well knew that the visits of insects were in- 

 dispensable for their fertilization " ; but Darwin 

 could not believe in so gigantic an imposture. 

 "Notwithstanding these several facts," he went 

 on, " I still suspected that nectar must be 

 secreted by our own orchids, and I determined 

 to examine O. morio rigorously. As soon as 

 the flowers were open I began to examine them 

 for twenty-three consecutive days; I looked at 

 them after hot sunshine, after rain, and at all 

 hours; I kept the spikes in water and examined 

 them at midnight and early the next morning." 

 He irritated the nectaries with bristles and ex- 

 posed them to irritating*vapors. He examined 

 flowers whose pollinia had been removed, and 

 others which would probably have them soon 

 removed. But the nectary was invariably dry. 

 Only after he had made the negative evidence 

 as complete as it could be made, by examining 



