1895.] NATURAL SCIENCES OF PHILADELPHIA. 555 



NOTES ON THE STUDY OF THE CROSS-FERTILIZATION OF FLOWERS 



BY INSECTS. 



BY IDA A. KELLER. 



One of the most remarkable discoveries in plant physiology was 

 certainly that of the cross- fertilization of plants by the aid of insect 

 visitors. That this discovery, made toward the end of the last 

 century, was founded upon actual fact has been verified by almost 

 every one who has become interested in this most remarkable 

 phenomenon. Apparent as it is in many cases, in more instances, 

 cross-fertilization by means of insects is simply a conjecture. There 

 is no more fruitful source of error, perhaps, in the experience of all 

 scientific knowledge than a sudden brilliant discovery, which is 

 founded upon careful observations in a limited number of cases, and 

 the wholesale application of its results without the exercise of suf- 

 ficient caution. Again and again, the organic world has been shown 

 to be so complex that no one simple formula can be found to express 

 adequately the exact situation in each of a great variety of cases. 

 Experience is constantly showing that each particular case must be 

 carefully studied by "itself before we can with any degree of certainty 

 gain a thorough understanding of any general phenomenon in plant 

 or animal life. 



In my attempts to obtain an impartial view of the subject of cross- 

 fertilization, so far as the actual observations made in this field up to 

 the present day will permit, I was struck with a number of curious 

 facts in connection with the development of our knowledge in this 

 direction. I must, however, apologize for the rather meagre pre- 

 sentation of the subject. I have had neither the time nor the op- 

 portunity to acquaint myself thoroughly with its entire literature, 

 and the original observations which I have made in this line are 

 limited in number. 



Conrad Sprengel, as we all know, discovered " The Secret of 

 Nature Revealed in the Formation and Fertilization of Flowers." 

 Over one hundred years have passed since this was recorded, and 

 yet the plant world offers in this respect one puzzle after another. 



