RAR* 



NEW YORK 

 BOTANIC Al 



■ ■ 



AFTER-RIPENING AND GERMINATION OF 

 JUNIPERUS SEEDS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 275 



Dean A. Pack 



(with ONE figure) 



Some seeds fail to germinate in compensating percentages or 

 even at all when placed under ordinary germination conditions. 

 Because of inquiries directed to this laboratory from various 

 growers concerning the best methods of handling juniper seeds, 

 there was conducted a careful study of after-ripening, germination, 

 and seedling development, as well as some of the chemical and 

 physiological changes involved in these processes. Strict quaran- 

 tine laws, recently put into effect, will mean that many species of 

 decorative plants that were formerly grown from seeds in foreign 

 countries and brought to America as plants, must now be grown 

 from seeds by American nurserymen. This will doubtless promote 

 study of the germinative behavior of many refractory seeds in the 

 future. 



Literature 



Wild plants of the temperate zone produce seeds that usually 

 have a rest period, which varies as to length and cause with the 

 different species and kinds of seeds. This dormancy is found to 

 be characteristic of the seeds of 75 per cent of the wild and the 

 cultivated plants studied by Howard (18). Although the rest 

 period of most seeds is only a few months, it may be years, as in 

 the case of some Conifers (21) and of Euphorbia Cyparissias (19). 

 Crocker (5) states that delayed germination is due to one or more 

 of the following conditions : (1) rudimentary embryo, (2) dormant 

 embryo, (3) coats inhibiting embryo expansion, (4) coats inhibiting 

 gas exchange, (5) coats inhibiting water absorption, (6) a combina- 

 tion of two or more of these, and (7) secondary dormancy. Up 



04 to date seeds have been studied that represent each of these differ 



2 ent types of dormancy. 



^ Botanical Gazette, vol. 71] [32 



