On Spontaneous Generation. 377 



where the same sort of water forms natural puddles, and the 

 clay ends over a stratum of sandy loam. But they are not 

 found higher up the limestone hill, nor on the sand-stone 

 mountains in any part of the alpine district, which is farther 

 behind. Their seeds cannot, therefore, have been floated to 

 the new locality by the water, nor can I conceive how they 

 could have been carried there by birds. 



I have, without exception, found Hypericum liumifusum 

 growing first on the circumference of that circular mound, ele- 

 vated above the level of irrigation of the adjacent district, 

 where coal-burners had charred resinous wood, provided the 

 mound consisted of that sandy soil which naturally covers it- 

 self with heather. I cannot state the precise time when the 

 Hypericum first appears, after the mound has been left by the 

 coal-burners ; but it always first shows itself on the limits of 

 the black disk formed by pieces of charcoal that have been 

 left, after the clamp has been removed, therefore on the spot 

 where the decomposition of the charcoal first takes place, and 

 as that decomposition proceeds towards the centre, the plant 

 overruns the whole mound. As long as the clamp, or char- 

 coal kiln, is in operation, there is no trace of the Hypericum, 

 and it afterwards first shews itself on spots that have been ex- 

 posed to a heat sufficient to kill any seeds that may have been 

 in the ground. The water from the neighbouring ground 

 having no access to the spot, and the seeds of the Hypericum 

 not being furnished with a pappus or wings, I do not see how 

 we are to account for this phenomenon, except by the gene- 

 ratio (Bquivoca, and this being granted, can we be accused of 

 speculating too wildly, if we venture the opinion, that the ori- 

 ginal generation of the plant took place under analogous cir- 

 cumstances, for instance, when in a temperate climate, a fir 

 wood, growing in a sandy locality, had been set on fire by 

 lightning, and partially consumed ? 



Similar considerations lead me to suppose, that certain 

 plants which are mostly and almost exclusively found on spots 

 where ruins are mouldering, or buildings have formerly stood, 

 and where the rubbish of human constructions is mixed with 

 the natural constituents of the ground, have been first gene- 

 rated within man's existence. Even admitting this, it would 

 doubtless be difficult to point out exactly the species to which 

 such an origin may be ascribed, as they must have spread to 

 other localities, not capable of effecting their spontaneous 

 generation, but capable of developing their seeds into perfect 

 plants. Hyosciamus niger, Senecio viscosus, and Echium vul- 

 gare, have struck me as possible instances, but this origin ap- 

 peared to me probable as to a rare plant, Asperugo procumbens, 



