POLLINATION 303 



now know that cross-fertilization is exceedingly com- 

 mon among hermaphrodites, but we have also learned 

 that, wonderful as are the devices in many such flowers 

 which have relation to cross-fertilization, in the same 

 flowers there are devices, not one whit less wonderful, 

 by which self-fertilization is achieved, either in supple- 

 ment to cross-fertilization, or to ensure the formation of 

 fertile seed in the event of its failure. Cross-fertiliza- 

 tion is so widespread that it must have an important 

 significance, for in Nature " nothing walks with aimless 

 feet. ' ' Probably its essential purpose is the maintenance 

 of a high standard in the race by avoiding degenera- 

 tion due to inbreeding. Contrary to common thought, 

 inbreeding is not disastrous if the parents are healthy; 

 but if parents are not sound, the progeny must suffer. 

 Cross-breeding may modify or even destroy weak char- 

 acters and ominous tendencies. There may be dangers 

 ahead for self-fertiHzed plants, no matter how healthy 

 and successful they are at present ; but at any rate they 

 run no risk of failure to ripen seed so long as they 

 remain sound, and they are able to achieve that im- 

 portant end with great economy so far as the expendi- 

 ture of pollen is concerned. In their case a little pollen 

 goes a long way, and wastage is infinitesimal. 



Always remembering that pollination is preliminary 

 to fertilization, and that cross-fertilization depends upon 

 the successful transfer of poUen by some agency from 

 one flower to another, we will now note the agencies 

 involved, and some out of the many devices that have 

 been elaborated in relation thereto. 



Water, which is of prime importance in the sexual 

 intercourse of Algae, is used as a pollinating agent by 



