STUDIES OF NATUEAL AND ARTIFICIAL PAR- 

 THENOGENESIS IN THE GENUS 

 NICOTIANA. 1 



RICHARD WELLINGTON 



Associate Horticulturist, New York Agricultural 

 Experiment Station 



Parthenogenesis is a phenomenon that is known to 

 exist in many widely separated genera of the higher 

 plants. In but few cases does it seem likely that the 

 regular reduction of gametogenesis with the subsequent 

 nuclear fusion of fertilization never occurs, yet it is 

 probable — from the frequent discovery of new examples 

 —that it will ultimately be found that the ability to dis- 

 pense with typical sexual reproduction is comparatively 

 common. Should this prove to be the case, one would 

 forced to conclude that sexual reproduction was d 

 oped for reasons other than protoplasmic necessity, 

 Maupas and his followers would have biologists believe. 



This is the fundamental problem toward the solution 

 of which all data on parthenogenesis contribute, but 

 pending the time when it can be discussed intelligently, 

 there are sub-questions that are not without their inter- 

 est. Loeb's researches have shown that the stimulus to 

 development which is an attendant result of fertiliza- 

 tion, is physico-chemical. Observations on several 

 genera of parthenogenetic insects have shown that the 

 presence or absence of sexual reproduction is largely de- 

 pendent upon external conditions such as food, light, 

 temperature, etc. Little is known of the role played by 

 such stimuli in parthenogenesis in plants, however, al- 

 though knowledge on the subject is of some import aside 



Harvard University!" 1 ^ Lab ° rat ° 17 ° • 

 279 



