GENEEAL PRINCIPLES AND METHODS. 141 



it will be favorable for the germination of seeds of plants 

 indigenous to cool climates ; but a temperature of sixty 

 to seventy degrees will be none to high for ordinary green- 

 house plants ; while seeds from the tropics may need ten 

 or twenty degrees higher temperature. 



While it is generally conceded that new seeds are pref- 

 erable to old ones, still the idea of newness should not 

 mislead the propagator and cause him to employ imma- 

 ture seed ; for, in many instances, what would be consid- 

 ered a fully ripe seed has not arrived at its best condition 

 for sowing or growth. Seeds containing a large amount 

 of natural moisture, or sap, will often fail to grow if 

 placed in the ground when new and fresh ; bnt if left to 

 dry a few weeks or months and then sown, they will ger- 

 minate freely. I am unable to give any scientific reason 

 for these variations, but have learned from long experience 

 that while freshly gathered seeds of some kinds of plants 

 will fail to grow, after having been dried for some time 

 they germinate very readily. It would appear that the 

 loss of natural moisture and shrinking increases the power 

 of absorbing external moisture, and accelerating the 

 chemical changes that take place during germination. 

 But if the drying is allowed to proceed too far, the vital 

 energies are diminished or wholly destroyed. A period 

 of rest appears to be necessary to the seeds of a large 

 majority of plants, while, on the contrary, there are kinds 

 which must be placed in a pofition for growth before 

 losing much of their natural moisture, else they fail to 

 germinate. For instance, the seeds of our indigenous 

 White Maple {Acer dasycarpum), and those of the Eed 

 Maple [A. rubrum), will not withstand drying, and must 

 either grow within a few days after falling from the tree 

 or perish. But of the seeds of the Elm ( Ulmus), of 

 various species, ripening at the same time as the Maples 

 named, and also similar in structure, some will sprout 

 immediately, while others remain dormant until the fol- 



