I40 Outline of Genetics 



that actually accounts for the results in the matter. Through 

 careful sections of stigmas made at intervals, East discovered the 

 following fact. Own pollen germinates on own stigmas just as 

 readily as does foreign pollen, and the first increment of growth of 

 the two types of tubes takes place at the same rate. After that 

 own pollen tubes continue to grow steadily and "normally" at 

 the same rate at which they started, but the rate of growth of 

 foreign pollen tubes is continuously accelerated, as though they 

 were receiving some stimulus which was ineffective on own pollen 

 tubes. The result is that own pollen tubes fail to reach the ovary 

 before the stigma and style have decayed, while foreign pollen 

 tubes, with their accelerated growth, ''reach the goal before the 

 road has become blocked." 



LITERATURE CITED 



1. Allard, H. a., and Garner, W. W., Flowering and fruiting 

 of plants as controlled by length of day. U.S. Dept. Agric. 

 Yearbook, 1920. pp. 377-400. 



2. Belling, John, K study of semi-sterility. Jour. Heredity 

 5:65-75. 1914. 



3. , A hypothesis of semi-sterility confirmed. Jour. 



Heredity 7:552. 1916. 



4. East, E. M., and Park, J. B., Studies on self-sterility. I. 

 The behavior of self-sterile plants. Genetics 2:405-609. 



1917. 



5. , Studies on self -sterility. II. Pollen tube growth. 



Genetics 3:353-366.^^5. 3. 1918. 



6. East, E. ISI., Studies on self -sterility. III. The relation 

 between self-fertile and self-sterile plants. Genetics 4:341- 



345- 1919- 



7. Eyster, W. H., The linkage relations between the factors for 



tunicate ear and sugary endosperm in maize. Genetics 6: 

 209-240. 192 1. 



8. Gravatt, F., a radish-cabbage hybrid. Jour. Heredity 5: 

 269-272. 1914. 



9. Moore, C. W., Self-sterility. Jour. Heredity 8:203-207. 

 1917. 



