On the Cross- Fertilization of Flowers hij Insects. 249 



XXXV. — Notes on the Stadi/ of the Gross-Fertilization of 

 Floiccrs hy Insects. V>y Ida A. Keller, Ph.D.* 



OxE of tlie most remarkable discoveries in plant-physioloo'y 

 was certainly that of the cross-fertilization of plants by tiie 

 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 oP 

 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 

 sufficient 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 ci'oss-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 connexion with the development 

 of our knowledge in this direction. I must, however, apolo- 

 gize for the rather meagre presentation of the subject. I 

 have had neither the time nor the opportunity to acquaint 

 myself thoroughly with its entire literature, and the original 

 observations v/hich I have made in this line are limited in 

 number. 



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

 of Nature lievealed 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. Instead of having exhausted the 

 study of the subject by this time, it seems to be gaining in 

 interest. 



Naturally enough, it was not the tendency of scientists to 

 try to disprove what was evidently true from the observations 



* From the ' Proceedings of the Academy of Natural Scieuces of 

 Philadelphia,' 1895, pp. 555-561. 



Ann. & Mag. }^. Hist. Ser. 6. Vol. ■s.yW. 17 



