AMERICAN JOURNAL OF BOTANY 



[Vol. 8, 



because of the difficulty of getting large quantities of material, as Heyl 

 points out when he estimates that it takes 610 million grains of ragweed 

 pollen to make a gram. 



Table 5. Kammann's {191 2) Analysis of Rye Pollen {figures indicate percentages) 



Inorganic substances l 3-5° 



Water 10.18 



Ash 3-4 



Organic substances 86.42 



Alcohol-ether-soluble 3- 



Carbohydrate 2 5- 



Non-protein nitrogen 18. 



Protein 4°- 



Table 6. Koessler' s (1918) Analysis of Ragweed Pollen (figures indicate percentages} 



Inorganic substances 21. 1 



Moisture 10.5 



Ash 10.6 



Organic substances 78.9 



Total reducing sugars after hydrolysis 6.89 



Ether-soluble lipoids 10.3 



Fatty acids after hydrolysis 4.75 



Phytosterol 0.34 



Insoluble in ether but soluble in 95 percent alcohol 12.5 



Extractives, etc., soluble in alcohol (resins) and water 11.5 



Insoluble residue (crude fiber, proteins, etc.) 37-71 



Table 7. Purin Bases and Amino Acids in Pollen 



Other Physiological Aspects of Pollen in which Enzymes may Play a Part 



In certain flowers there are two kinds of pollen grains, some of which 

 produce tubes and others which do not. Miiller (1883, p. 242) first 

 distinguished these as " Befruchtungs"- and " Bekostigungs "-pollens, the 

 former being the fertile, and the latter the sterile pollen which Miiller 



