1918] Kendall: Abscission of Flowers and Fruits in Solan-aceae 391 



criterion of age — upon which the test was being made. This was done 

 by noting on the tag which was supplied for each flower (ef. page 385) 

 the length of the corolla in millimeters, the condition of the corolla, 

 or any other condition of the flower which would serve to indicate its 

 age. The period of development of the flower and fruit is divided 

 into several arbitrary stages, each of which is designated by a Roman 

 numeral in the second column of the tables. Where the number of 

 flowers designated in the first column are nearly in the same stage 

 of development only one numeral appears in the table, but where the 

 range in size of the flowers is quite extensive two numerals appear, 

 representing the range in size within which the flowers were found at 

 the time of the experiment. The stages of floral development which 

 each Roman numeral represents are given below. 



Bud 



I corolla 2 mm. to 5 mm. in length 



II corolla 6 mm. to 10 mm. in length 



III corolla 11 mm. to 15 mm. in length 



IV corolla 16 mm. to 20 mm. in length 



V corolla 21 mm. to 30 mm. in length 



VI corolla 31 mm. to 40 mm. in length 



VII corolla 41 mm. to 50 mm. in length 



Flower 



VIII corolla opening 



IX anthesis 



X 2 days after anthesis 



XI corolla withering 



Fruit 



Immature 



XII fruit 5 mm. to 8 mm. in length 



XIII fruit 9 mm. to 10 mm. in length 



Mature 

 XIV fruit 11 mm. to 12 mm. in length 



The operation of injuring the flower consisted largely in removing, 

 by cutting away with a sharp safety razor blade, entire floral organs 

 or parts of them. In some cases, however, organs were only slit longi- 

 tudinally with a sharp knife or merely punctured with the point of a 

 pair of forceps. 



Several types of injury that remove the style, stigma or stamens 

 before pollination may cause fall by preventing fertilization. It is 

 evident, therefore, that fall occurring after such an operation per- 

 formed on the flower before anthesis may be due to lack of fertiliza- 

 tion and not to the injury. If, however, the fall occurs within the 

 minimum time elapsing between anthesis and normal flower-fall due 



