No. 507] BOTANICAL SOCIETY OF AMERICA 



L37 



The methods by which the problems were attacked 

 were neither many nor complicated. Patience and fore- 

 thought and perseverance are their chief characteristics. 

 Observation, not exclusive of any discernible fact; ex- 

 perimentation, with control of the incidental results of 

 manipulation; testing the parent condition of seeds sup- 

 posed to be pure; consideration of alternative explana- 

 tions of phenomena, and especially of those opposed to 

 the conclusions adopted; counting, weighing, measuring 

 —almost beyond belief; ingenious substitutions for in- 

 sects in laboratory and garden observations on struc- 

 tures concerned in pollination ; watching insects at work 

 on flowers and supplementing such observation by nota- 

 tion of the record of their visits afforded by the flowers 

 themselves; confirming the identity of doubtful pollinia 

 on a moth by restoring their original color through 

 moistening them; field observations at all hours and 

 under all climatic conditions; ascertaining pollen-tube 

 development in prepotency questions ; painstaking polli- 

 nations to cover numerous permutations: such were the 

 methods. 



The results of Darwin's work in this field are not easily 

 epitomized. It is not going too far to say that he secured 

 universal recognition of SprengePs unheeded demonstra- 

 tion that the structure of many flowers serves to ensure 

 their pollination by unconscious insect aid ; he broadened 

 this by enough detail to warrant the conclusion that in 

 general it serves to ensure cross-pollination by such aid, 

 in this way substantiating Knight's law 4 'nature intended 

 that a sexual intercourse should take place between neigh- 

 boring plants of the same species"; he gave experimental 

 demonstration of the benefits of crossing, not in itself, 

 but through the interbreeding of individuals which for 

 several generations have been subjected to slightly dif- 

 ferent conditions, or as he puts it, to "what we call in our 

 ignorance spontaneous variation"; and he showed at 

 once the utility of assured partial self-fertilization as 



