GEEMINATION. 315 



kinds of agricultural seeds that light exercises no appreci- 

 able iniluence of any kind on germination. 



The Time required for Germination varies exceedingly 

 according to the kind of seed. As ordinarily observed, 

 the fresh seeds of the willow begin to sprout within 12 

 hours after falling to the ground. Those of clover, wheat, 

 and other grains, germinate in three to five days. The 

 fruits of the walnut, pine, and larch, lie four to six weeks 

 before sprouting, while those of some species of ash, beech, 

 and maple, are said not to germinate before the expiration 

 of 1^ or 2 years. 



The starchy and thin-skinned seeds quicken most readi- 

 ly. The oily seeds are in general more slow, while such 

 as are situated within thick and horny envelopes require 

 the longest periods to excite growth. 



The time necessary for germination depends naturally 

 vjpon the favorableness of other conditions. Cold and 

 drought delay the process, when they do not check it al- 

 together. Seeds that are buried deeply in the soil may re- 

 main for years, preserving, but not manifesting, their vital- 

 ity, because they are either too dry, too cold, or have not 

 sufficient access to oxygen to set the germ in motion. 



To speak with precision, we should distinguish the time 

 from planting the dry seed to the commencement of germ- 

 ination which is marked by the rootlet becoming visible, 

 and the period that elapses until the process is complete, 

 i. e., until the stores of .the mother-seed are exhausted, 

 and the young plant is wholly cast upon its own resources. 



At 41° F. in the experiments of Haberlandt, the rootlet 

 issue'd after 4 days, in the case of rye, and in 5-7 days in 

 that of the other grains and clover. The sugar-beet, how- 

 evei-, lay at this temperature 22 days before beginning to 

 sprout. 



At 51°, the time was shortened about one-half in case 

 of the seeds just mentioned. Maize required 11, kidney- 

 beans 8, and tobacco 31 days at this temperature. 

 Digitized by Microsoft® 



