PROLONGED VITALITY OF SEEDS. 289 



lity, that is, their power of performing their vital operations, 

 when placed in the proper circumstances. And even if moisture 

 or oxygen be not entirely excluded, the same effect may result, 

 provided that the temperature be low and uniform. Thus the 

 seeds of most plants may be kept for several years, freely ex- 

 posed to the air ; provided they are not exposed to dampness, 

 which will cause them either to germinate, or to decay. Some 

 of those, which had been kept in seed-vessels of plants preserved 

 in the herbarium of Tournefort, a French botanist, were found 

 to retain their fertility, after the lapse of nearly a century. 



447. Instances are of no unfrequent occurrence, in which 

 ground, that has been turned up, spontaneously produces plants 

 different from any in their neighbourhood. There is no doubt 

 that, in some of these cases, the seed is conveyed by the wind, 

 and becomes developed only in spots, which afford it congenial 

 soil ; as was formerly mentioned in regard to the spores of the 

 Fungi (. 50). Thus, it is commonly observed, that clover is 

 ready to spring up on soils, which have been rendered alkaline 

 by the strewing of wood-ashes, or the burning of weeds, or 

 which have had the surface broken and mixed with lime. But 

 there are many authentic facts, which can only be explained upon 

 the supposition, that the seeds of the newly-appearing plants 

 have lain for a long period imbedded in the soil, at such a dis- 

 tance from the surface, as to prevent the access of air and mois- 

 ture ; and that, retaining their vitality under these conditions, 

 they have been excited to germination by exposure to the atmo- 

 sphere. The following possesses considerable interest. 



448. To the westward of Stirling, there is a large peat-bog, 

 a great part of which has been flooded away, by raising water 

 from the river Teith, and discharging it into the Forth ; the 

 object of this process being, to lay bare the under-soil of clay, 

 which is then cultivated. The clergyman of the parish was on 

 one occasion standing by, while the workmen were forming a 

 ditch in this clay, in a part which had been covered with four- 

 teen feet of peat earth ; observing some seeds in the clay, which 

 was thrown out of this ditch, he took them up and sowed them ; 

 they germinated, and produced a species of Chrysanthemum. 



