268 General Botany 



that is, place them under a thin layer of soil over winter. In 

 the spring they germinate readily. The same seeds kept at 

 room temperature and then planted will not germinate for a 

 much longer period. A low temperature (about 40° F.) is most 

 favorable for the development of acidity in the growing embryo. 

 Acidity favors growth because it increases the ability of the cells 

 to take up water, and it favors the production and activities of 

 enzymes that are necessary for digestion, assimilation, and 

 respiration. 



5. Imperfectly developed embryos. A fifth form of dormancy 

 occurs in many seeds in which the embryo is only partly developed 

 when the seed matures. Sometimes it is little more than a 

 fertilized egg; but one may find all gradations between these 

 few-celled embryos and those that are nearly or completely 

 grown. They occur among a wide range of plants, but most of 

 these plants are not commonly known, except the ginkgo, holly, 

 buttercup, dogtooth violet, and many orchids. Orchid seed, 

 formerly thought to germinate only in the presence of certain 

 fungi, may be germinated in a sugar solution, which furnishes 

 both the water and the food material necessary to complete the 

 growth of the embryo. 



Longevity of seeds. How long do seeds live in a dormant con- 

 dition? This question is frequently asked, and in connection 

 with it there are many stories told that are either based on wild 

 guesses or are merely fiction. Unscrupulous individuals have 

 at times taken advantage of people by these fictitious stories and 

 made large profits by selling small vials of ordinary seeds at high 

 prices. '' Miracle " wheat, purporting to have been taken from 

 mummy cases in Egypt, had a wide sale among unsuspecting 

 farmers until investigation showed the true source and the 

 worthlessness of the seeds. 



There are few unquestionable records of seeds germinating 

 after 100 years of dormancy ; even those germinating after 

 periods much shorter than 100 years are rare. The seeds of a 



