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 Howarp (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 
to date seeds have been studied that represent each of these differ- 
ent types of dormancy. 
Botanical Gazette, vol. 71] [32° 
