4 Sudden Appearance of Plants. 
flowers in its second year, I find from a comparison of dates that 
the first year’s plants must have made their appearance in the 
year in which the road was made, thus rendering it improbable 
that the seeds were derived from the plants already in existence, 
and of which there were only one or two on the island. Ina 
reply to that letter, Mr. J- C. Shenstone mentions a case from his 
own experience which also tends to confirm the buried-seed theory. 
There need be little difficulty in accounting for the presence 
of dormant seeds in the soil. Let it be granted that at one time 
some given species were common in a district ; through the exhaus- 
tion of the soil, however, they gradually died out, that is, a smaller 
number of plants appeared. This could only have arisen from the 
fact that a smaller number of seeds germinated; there would, 
therefore, be left a number of seeds capable of germinating, and 
only waiting for suitable conditions to enable them to do so. 
Most of the seeds which did not germinate, and remained at the 
surface, would undergo the ordinary process of decay. Many, 
however, would find their way to greater depths, some of them 
being washed down by water, others, and I think the greater num- 
ber, would fall into the numerous cracks which are found on most 
lands after continued dry weather, a not uncommon condition in 
autumn. ‘The mere fact that this cracking process takes place 
most abundantly in the fruiting season renders this hypothesis, at 
least, highly probable. On the return of wet weather the cracks 
would close up, and the seeds would be preserved until the soil 
was turned over. Their germination would be prevented by the 
exclusion of air and light, and for the same reason they would not 
undergo decay. One difficulty is, that under ordinary conditions 
seeds only retain their power of germinating for limited periods, 
but under the conditions which hold here, I think it not by any 
means improbable that they will retain their vitality for much longer 
periods. 
Even if it were admitted that most cases of the phenomenal 
appearance of plants on newly turned soil were to be traced to 
dormant seeds derived from an earlier flora, it does not follow 
that in certain cases there are not other causes at work. For 
instance, seeds may be brought at times by animals and by the 
wind, and would naturally germinate more vigorously on fresh 
than on crowded soil, but 1 think such cases are exceptional. One 
very remarkable case of the agency of the latter is, however, found 
in a species of Sezecio, known in ‘Tasmania as “ fire-weed.” ‘This 
plant makes its appearance on patches of land that have been 
cleared by fire, and on those patches only. Mr. Wallace mentions 
a case in which a burnt patch, thirty-five miles into the virgin 
forest, and consequently that distance from the nearest Seneczo, 
immediately produced its crop of fire-weed. 
