﻿ADAMS— POLLEN GRAINS 



147 



3. Some pollen grains of apple germinated in tap water and 

 also in various strengths of sugar solution up to 50 per cent; the 

 pollen grains of black currant germinated in tap water and also 

 in 4, 8, and 16 per cent sugar solution. 



4. Some pollen grains of apple germinated in 12 hours, the 

 temperature ranging between 3?5 and f C. 



5. The quickest growth of the pollen tube observed was 651 .3 n 

 in 6 hours in apple, and 668 ju in 6 hours in black currant, as meas- 

 ured between perpendicular lines. 



6. Some varieties of the same species appeared to have more 

 vigorous pollen grains than others. 



7. The pollen grains germinated alike in light and darkness. 



8. Of the temperatures employed, 21-23 0 C. gave the quickest 

 germination. 



9. A few pollen grains of apple formed short pollen tubes after 

 being kept dry for about 3 months, and of pear after 10 weeks. 

 The pollen grains of strawberry, loganberry, and raspberry were 

 all dead after 2 months, and of black currant after 11 weeks. 



LITERATURE CITED 



1. Pfeffer, W., Physiology of plants. Eng. ed. 3 vols. 1900-1906. 



2. Jost, L., Zur Physiologie des Pollens. Ber. Deutsch. Bot. Gesells. 23: 

 504-515. 1906. 



3. Sandsten, E. P., Some conditions which influence the germination and 

 fertility of pollen. Univ. Wise. Agric. Exper. Sta. Research Bull. 4:149- 

 172. 1909. 



4- Craxdall. C. S., The vitality of pollen. Proc. Soc. Hort. Sci. 9:121-130. 



5. Martin, J. X., The physiology of the pollen of Trifolium pralense. Bot. 

 Gaz. 56:112-126. 1913. 



6. Chandler, W. H., The killing of plant tissue by low temperature. Univ. 

 of Missouri Agric. Exper. Sta. Research Bull. 8:141-309. 1913. 



