CHEMOTROPIC MOVEMENTS OF POLLEN TUBES 6 1 



and 4 or 5 g. cane sugar to 50 cc. distilled water. Warm until a 

 homogeneous solution is obtained. Place a drop of this solution 

 on a glass slip and when cold add a number of pollen cells of 

 Narcissus, Fritillaria, or Lathyrus. Cover with a thin circle of 

 glass and set in a moist chamber kept as near 18 C. as possible. 

 Examine eight or ten hours later, and also the next day. Note 

 the direction taken by the pollen tubes. All seem to be pointed 



FIG. 26. Chemotropism of pollen tubes. The lines a to b represent the edge of 

 a cover-glass under which are pollen tubes. In a, pollen of Narcissus tazetta in a 

 seven per-cent. solution of sugar is seen to be negatively chemotropic to the air at the 

 edge of the cover-glass. In b negative chemotropism of pollen tubes of Cephalan- 

 thera pallens in seven per-cent. sugar solution is shown, about 20 hours after begin- 

 ning of experiment, c, stigma of Narcissus tazetta with pollen tubes impinging on its 

 surface. After Molisch. 



toward the center of the preparation, or away from contact with 

 the air. Make a second preparation and treat it as the first but 

 seal the edges of the cover with vaseline. Compare the behavior 



