132 



pine forest is enormous. It gives rise to the so-called 

 'showers of sulphur' which everyone has heard of." Myriads 

 of the pollen grains are scattered by the winds to one which 

 reaches the stigma to fertilize the ovule. In close fertilized 

 flowers a small amount of pollen is produced. Now in the 

 contrasted case, that of pine trees, the vast superabundance 

 of pollen would be sheer waste if the intention was to fertilize 

 the seeds of the same tree.. 



Wallace says.'® "The facts as to the cross-fertilization of 

 flowers which have been briefly summarized, taken in con- 

 nection with Darwin's experiments proving the increased 

 vigor and fertility given by cross-fertilization, seem amply to 

 justify his aphorism, 'Nature abhors self fertilization,' and 

 his more precise statement, 'No plant is perpetually self- 

 fertilized." " 



c.i« n ..■ *j In fhe flowers considered so far the in- 



tent appears to be to secure cross 

 pollination, but there are many plants in which self-pollina- 

 tion is the rule. This is unknown in autogamy. Autogamy 

 cannot, of course occur in any other but perfect flowers. 



In Adoxa moschatteUina the flowers are proterogynous. 

 When the stigmas are receptive the anthers are short; they 

 lengthen out and flnally leave some of the pollen on the 

 stigma. If cross-pollination has not occurred, there are still 

 chances for self-pollination. In the early flowers of some 

 species of Geranium the flve stigmas are receptive. The 

 anthers, of which there are ten, have not dehisced. In a day, 

 or less in some cases, the anthers discharge their pollen on 

 the stigmas. The flowers close at night, and the following 

 morning the flve stamens next to the corolla lengthen, 

 straighten out and deposit their pollen on the stigmas. 



16 Darwinism, see page 221. 



