HISTORICAL SKETCH 



of interaction between the stamens and carpels is necessary for 

 the production of seed-bearing fruits. 



About sixty-five years later, Joseph Gottlieb Kolreuter (1761), 

 physician and professor of natural history at Wurtemberg, published 

 four parts of a treatise dealing with his experiments on sex in plants. 

 He fully confirmed the work of Camerarius and gave a detailed ac- 

 count of the importance of insects in flower pollination. He also 



produced hybrids in Nicotiana, 



Dianthus, Matthiola, and Hyo- 

 scyamus and showed that if the 

 stigma of a plant received its own 

 pollen and that of another species 

 at the same time, ordinarily the 

 former alone was effective. This, 

 he said, was the reason why hy- 

 brids were so rare in nature, al- 

 though they could be produced 

 artificially. 



Discovery of the Pollen Tube. 

 After the role of the pollen began 

 to be understood, the next step 

 was to determine the exact man- 

 ner in which it influenced the 

 ovule. Accident supplied the 

 starting point of some important 

 discoveries. An Italian mathe- 

 matician and astronomer named 

 Giovanni Battista Amici (1824), 



who was also a good microscope maker, found that the stigma of Portu- 

 laca oleracea was covered with hairs which contained some granules or 

 particles inside them. Curiosity prompted him to ascertain whether 

 they moved in the same way as the granules he had seen in the cells 

 of Char a. It pleased him to find that they did. While repeating 

 the observation, he accidentally saw a pollen grain attached to the 

 hair he had under observation. Suddenly the pollen grain split open 

 and sent out a kind of tube or "gut" which grew along the side of the 

 hair and entered the tissues of the stigma. For three hours he kept 

 it under observation and watched the cytoplasmic granules circulate 



Fig. 1. Giovanni Battista Amici. {Pho- 

 tograph obtained through the courtesy oj 

 Br. E. Battaglia.) 



