Decline of Growth and the Rest Period. Ill 



cies that do not germinate as soon as ripe, they imitate 

 nature by the process known as 



169. Stratification of Seeds. This consists in mix- 

 ing the freshly-gathered seeds with sand, taking care 

 that the sand is kept moist until the time for sowing 

 arrives. Large quantities of seeds may be stratified in 

 boxes, by placing the moist sand and seeds in alternate 

 layers, or the layers may be built up in a pile on the 

 ground. The sand should be coarse enough to admit 

 some passage of air between the particles and to give 

 perfect drainage. The layers should not much exceed 

 an inch in thickness, except for the larger seeds, and the 

 number of layers should not be so large as to prevent 

 proper aeration of the mass. Small quantities of seeds 

 may be mixed with sand or porous loam in flower-pots. 

 Moisture may be maintained in the boxes or pots by 

 burying them a foot or more deep in the soil in a well- 

 drained place, or by storing them in a moist cellar. 

 Care is necessary to keep mice and other vermin from 

 stratified seeds. It is well to cover pots in which valu- 

 able seeds are stratified, with a sheet of tin or zinc; 

 metal labels are best for distinguishing different sorts 

 of seed. The seeds should remain stratified until sow- 

 ing time, when they may be sifted out of the sand or 

 sown with it, as is more convenient. Seeds that do not 

 germinate well until the second spring after maturity 

 (162) are commonly left in stratification until that time. 



SECTION XIII. THE DECLINE OP GROWTH AND THE 

 REST PERIOD. 



170. Annual plants usually perish soon after matur- 

 ing their seed. In other plants, a certain period of 



