POLLEN AND PISTILS OP APPLES 409 



No secretions were found on the stigma when conditions were 

 most favorable for pollination. The favorable location of the 

 pollen grains on the stigma was found to be between the pa- 

 pillse. When so located they absorbed the required amount of 

 water and germinated. The pollen on the ends of the papillae 

 was observed in nearly all cases to remain plasmolyzed. 



Department of Botany^ 

 Iowa State College. 



LITERATURE CITED. 



1. Adams, J., On the Germination of the pollen grains of Apple 



and other Fruit Trees: Bot. Gaz., 61, pp. 131-147, 1916. 



2. Burck, W., Preservatives on the Stigma against the Germina- 



tion of Foreign Pollen; Proc. Akad. Wet. Amsterdam, 3, 

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3. Chandler, W. H., The Killing of Plant Tissue by low tempera- 



ture: Univ. of Missouri Agr. Exp. Sta. Res. Bull. 8, pp. 

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pp. 121-130, 1912. 



5. Hansgirg, Anton. Beitrage zur B'iologie und Morphologie des 



Pollens: Sitzungsber. Kgl. Bohm. Gesell. Wiss. Prag., 23, 

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6. Hedrick, U. P., The Relation of Weather to the Setting of 



Fruit; With the Blooming Data for 866 Varieties of Fruit: 

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Gesells., 23, pp. 504-515, 1905. 



8. Kny, L., Um den Einfluss ausserer Krafte, msbesonodere der 



Schwerkraft, des Lichtes und der Beruhrung fester Korper 

 auf die Anlegung von Sprossungen thalloser Gebilde und 

 deren Langenwachstum: Sitzungsber. Bot. Verein. Branden- 

 burg, 23, 1881. 



9. Lidfors, Bengt, Zur Biologie des Pollens: Jalirb. Wiss. Bot. 29, 



pp. 1-38, 1896. 



10. , Weitere Beitrage zur Biologie des Pollens: Jahrb. 



Wiss. Bot. 33, pp. 232-312, 1899. 



11. Leswis, C. I., and Vinceni, C. C'., Pollination of the Apple: 



Oregon Agr. Coll. Exp. Sta. Bull. 104, pp. 1-140, 1909. 



12. Mangin, L., Recherches sur le pollen: Bull. Soc. Bot. France, 



III, 32, pp. 337-342, 512-517, 1886. 



13. 3Iartin, J. N., The physiology of the Pollen of Trifolium 



pratense: Bot. Gaz., 56, pp. 112-126, 1913. 



14. , Relation of Moisture to Seed Production in Alfalfa: 



Iowa Agr. Exp. Sta. Res. Bull. 23, pp. 302-324, 1915, 



15. Mohl, , Beitrage zur Anatomie und Physiologie, I. Bern, 



1834. 



