DORMANCY OF BUDS 637 



years old and may have been 200 to 400 years old (Ohga, 1927). With this 

 one exception all the authentic records of seeds living for 75 years or longer 

 are of legumes. Further data on the longevity of seeds are given by Crocker 

 (1938). 



At least some of the seeds of a number of species of wild plants will 

 remain viable for 50 years or more. This is especially true of hard-coated 

 species. As a general rule only seeds with a pronounced dormancy remain 

 viable very many years in nature. The seeds of many weed species are 

 notoriously long-lived as compared with the seeds of most crop plants. This 

 is illustrated by an experiment initiated by Beal at East Lansing, Michigan 

 in 1879. Seeds of twenty herbaceous species were mixed with sand and buried 

 in pint bottles. Twenty such bottles were prepared. Once every five or 

 ten years one of the bottles was excavated and the enclosed seeds tested for 

 their percentage of germination. Fifty years later seeds of five species re- 

 mained alive and showed the following percentages of germination : yellow 

 dock (Rumex crispus) 52 per cent, evening primrose (Oenethera biennis) 

 38 per cent, moth mullein {Verbascum blattaria) 62 per cent, black mustard 

 {Brassica nigra) 8 per cent, and water smartweed (Polygonum hydropiper) 

 4 per cent (Darlington, 1931). 



Dormancy of Buds. — The buds of many species of plants also exhibit the 

 phenomenon of dormancy. In spite of favorable environmental conditions 

 which often prevail the buds on woody plants of temperate zones do not 

 usually develop into shoots the same season they are formed. Some important 

 exceptions to this statement are discussed in the next chapter. The length 

 of time for which such buds retain their dormancy varies considerably accord- 

 ing to species. Howard (1910) has made a comprehensive study of bud 

 dormancy in a large number of species of woody plants, some of American, 

 some of European, and some of Asiatic origin. This investigation was con- 

 ducted in Missouri. Of 234 species collected, buds of 125 species developed 

 when branches were brought into a greenhouse between October 28 and No- 

 vember 4. Most of these were European or Asiatic forms. In other words 

 the buds of more than half of the species experimented with were not in a 

 dormant state on this date. A second collection of branches from 283 species 

 was brought into the greenhouse on January 8-10. Of these buds developed 

 on 244 species. On February 23 a third collection of 63 species was made 

 composed largely of kinds on which the buds failed to develop in the preced- 

 ing two tests. On this date buds developed on all but five of the species 

 collected. The results of this study indicate that the buds of some woody 

 species retain their dormancy much longer into the fall or winter than others 



