108 Principles of Plant Culture. 



168. Age of Seed as Affecting the resulting Crop. Seeds 

 grown the same or the preceding season produce, as a 

 rule, more vigorous plants than older seeds. They may 

 not, however, in all cases produce plants that are most 

 productive of fruit or seed, for excessive vigor is gener- 

 ally opposed to reproduction. Cucumber and melon 

 plants grown from seed three or four years old are often 

 more fruitful than those from fresh seeds. In crops 

 grown for parts other than fruit or seed, fresh seeds are 

 undoubtedly preferable, but in crops grown for seed or 

 fruit, fresh seed may not always give as large returns as 

 seed of some age. This subject needs further investiga- 

 tion. 



169. How Drying Affects the Vitality of Seeds. The 

 vigor of seeds is probably never increased by drying 

 them, but the seeds of most annual and biennial plants 

 may become air-dry without material loss of vitality. 

 The seeds of many shrubs and trees, however, lose vital- 

 ity rapidly by such drying and those of some species are 

 destroyed by it. In nature, seeds of the latter class are 

 usually dropped from the parent plant before becoming 

 dry and are soon covered by leaves or other litter that 

 keeps them moist. Nurserymen either plant such seeds 

 as soon as they are ripe, or if of species that do not ger- 

 minate as soon as ripe, they imitate nature by the process 

 known as 



170. Stratification of Seeds. This consists in mixing 

 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 



