STRATIFYING SEEDS. 



15 



at the top. In one of these a thermostat (c) is placed, 

 which controls the flow of gas at the jet beneath, and in 

 the other a thermometer (d) may be placed to show the 

 temperature of the water in the jacket." 



3. THE HANDLING AND SOWING OF 

 SEEDS AND SPORES. 



Preparatory Treatment of Seeds. — Many seeds demand 

 some treatment preparatory to sow- 

 ing. Nearly all hard and bony 

 seeds fail to germinate, or at least 

 germinate very irregularly, if their 

 contents are allowed to become 

 thoroughly dry and hard. The 

 shells must also be softened or 

 broken, in many cases, before the 

 embryo can grow. Nature treats 

 such seeds by keeping them con- 

 stantly moist under leaves or mold, 

 and by cracking them with frost. 

 This suggests the practice known 

 to gardeners as stratification, an 

 operation which consists in mix- 

 ing seeds with earth and expos- 

 ing them to frost or to moisture 

 for a considerable time. 



Stratification is practiced, as a 

 rule, with all nuts, the seeds of forest trees, shrubs, the 

 pips of haws and often of roses, and in many cases with 

 the seeds of common fruits. Seeds should be stratified 

 as soon as possible after they are mature. Small seeds 

 are usually placed in thin layers in a box alternating with 

 an inch or two of sand. Sometimes the seeds are mixed 

 indiscriminately in the sand, but unless they are large it 

 is difficult to separate them out at sowing-time. The 

 sand is often sown with the seeds, however, but it is 

 difficult in such cases to distribute the seeds evenly, and 



14. sprouting chamber. 



