76 



pollen can easily fall on the stigma, but Darwin and others 

 have shown that the pollen is quite inactive on its own stig- 

 ma, There is another important diflference. The pollen 

 gruin of the long-styled flowers is smaller, while the stigma 



OoOO 

 ° 



FIG, 29. 

 Fig. 29. Cowslip (Primulo). Left hand figure, long-styled flower ; right hand 

 figure, short-styled flower; a, stamens; co, corolla; 8t, style. PoUen^rains be- 

 tween. The smaller belonging to long-styled flower; the larger to short-styled 

 flower; magnified about 250 times. (After Lubbuck.) 



is larger. The pollen grains of the short-styled flowers are 

 larger, while the stigmas are smaller. Insects carry the pol- 

 len from the short-styled flowers and leave it on the long- 

 styled, while the pollen from the long is carried over to the 

 short. 



Darwin notes that iii Primula veris the corollas of the 

 two forms are difl'erent. He sums np the difference as fol- 

 lows: "The long-styled plants have a much longer pistil, 

 with a gobular and much rougher stigma, standing high 

 above the anthers. The stamens are short; the grains of 

 pollen smaller and oblong in shape. The upper half of the 

 tube of the corolla is more expanded. The number of seeds 

 produced is smaller and the ovules larger. 



The short-styled plants have a shorter pistil, half the 

 length of the tube of the corolla, with a smooth depressed 

 stigma standing beneath the anthers. The stamens are long; 



