30 PLANT PROPAGATION 



is practiced in warm climates where moisture in effect 

 takes the place of frost. 



This process of stratification depends for its utility 

 upon the osmotic passage of water into the seeds which 

 are thereby softened so the embryo can easily emerge. 

 In cold climates frost splits hard-shelled seeds, which in 

 nature are kept moist by the pulp 

 around them (peach, walnut) or by 

 fallen leaves which cover them (hickory, 

 chestnut). Many hard-shelled seeds 

 have a seam through which water en- 

 ters. Perhaps the majority of such 

 PLANT "protector sccds, if placed in the soil and kept 

 there through the winter, would be suf- 

 ficiently soft by spring, even without frost action, to ger- 

 minate readily. 



50. Stratification to maintain moisture in seeds (apple, 

 cherry) is often practiced even in cold climates. If such 

 seeds were allowed to dry out they would be useless. 

 Hence, as soon as gathered they are stratified, often 12 

 to 18 inches deep, so they will not sprout but will keep 

 moist until the autumn, when they are dug up and strat- 

 ified in the usual way. (Compare 54.) 



51. Nurserymen's stratification method. — Nurserymen 

 often stratify peach and plum seeds in shallow, bowl-like 

 pits or in trenches which hold many bushels. These are 

 covered with sand and protected as already described till 

 spring. The seeds are then sown after the sprout has 

 made a little growth. This method is better than sowing 

 the seeds in the nursery rows during the fall, because the 

 seeds can be better protected from animals and also be- 

 cause soil prepared in spring is less likely to bake than 

 that prepared in the fall. 



52. When to plant stratified seeds. — Stratified seeds 

 should always be planted early in spring before germina- 

 tion starts, because many species sprout while the ground 

 is still cold (pear, beech, oak, apple). If sprouting starts 



