tegration of its tissues; or it may be preserved 
| consequence of the absence of those agents 
_ which ordinarily excite decomposition. The 
Occasional suspension of vital action from a 
shange in the organism itself, appears usually 
to result from a general law of periodicity, 
ich affects, more or less, all organised 
beings, producing the phenomena of sleep, 
“hybernation, &c.; but it may also arise from 
_ particular causes operating within the system, 
‘aSin syncope. Each of these cases will now 
be separately considered. 
— Dormant vitality of seeds, eggs, &c.—The 
condition of organised beings of which we have 
to treat—that in which vital action is sus- 
ed from the absence of the stimuli ne- 
ry to maintain it, and vitality never- 
heless preserved—is manifested in the most 
 rema able manner by the reproductive germs 
which are periodically separated from plants 
it id animals, and which are endowed with the 
| power of developing themselves into new indi- 
_ viduals when the requisite conditions are sup- 
plied to them. In the lowest classes of each 
Kingdom, it would appear that these germs are 
liberated from the parent unprovided with any 
means for the continuance of their development ; 
|_and that from the first, therefore, they rely upon 
| the surrounding elements for al/ the conditions 
of their active existence. It is beautifully pro- 
vided that, in proportion to the probable defi- 
ciency of some of these, should be the tenacity 
with which the apparently lifeless germs re- 
tain their vitality. The sporules of the fungi, 
which can only subsist on decaying organised 
Matter, seem universally diffused through the 
atmosphere, and ready to vegetate with the 
most extraordinary rapidity whenever a fitting 
nidus is afforded for their development. This, 
at least, appears the only feasible mode of ex- 
plaining their appearance in the forms of mould, 
mildew, &c. on all decaying surfaces; and 
that there is no improbability in the suppo- 
sition itself is shown by the estimate of Fries, 
who states that a single individual of reti- 
ularia maxima will emit above 10,000,000 of 
these germs, so minute as when collected to 
be scarcely visible to the naked eye, rather re- 
sembling thin smoke, and so light as to be 
wafted by every movement of the atmosphere, 
so that, he remarks, “ it is difficult to conceive 
a place from which they can be excluded.” 
Itseems more than probable that in a similar 
Manner is to be explained the appearance of 
_ infusorial animalcules in all situations adapted 
_ to their existence; and that their germs are 
_ constantly and universally diffused through the 
_ air, ready to commence the active exercise of 
ieir dormant properties whenever they meet 
— the stimuli to their development afforded 
_ by warmth, moisture, and decomposing organic 
atter.* 
We have no means of ascertaining the 
length of time during which this dormant vi- 
_ tality may be preserved. It would be difficult 
-. assign a limit to it, since it is scarcely con- 
eivable that any change can occur in the struc- 
* For an important experiment on this subject 
} reeently performed by Schultz, sce Edinburgh Phi- 
_losophical Journal, Oct, 1837. 
LIFE. 
155 
ture of these minute desiccated points which 
they do not undergo during ihe first few 
hours of their aerial residence; and we have 
no reason to believe that vitality can be de- 
stroyed without change of structure. With re- 
gard to the seeds of phanerogamic plants, we 
have more certain evidence, and this of a very 
interesting character. It is to be remarked, 
however, that in them, as in the eggs of 
higher animals, there is, besides the germ it- 
self, a reservoir of nutriment supplied by the 
parent, which enables the germ to ¢ontinue its 
development up to the point at which it be- 
comes fit to maintain its own existence, with- 
out any other than the ordinary assistance of 
vital stimuli. The germination of a seed, for 
example, requires only warmth, moisture, and 
the access of air, and is further accelerated by 
the absence of light?“and the hatching of an 
egg is dependent only on a temperature more or 
less elevated and the presence of air. Hence 
the necessity for so great a tenacity of vitality 
as that possessed by the germs of the simpler 
classes does not exist, and although under 
favourable circumstances the vitality of seeds 
may be prolonged for an almost indefinite 
period, they are more susceptible of the inju- 
rious influence of external agents, and their 
fertility is destroyed by changes of condition 
which would have no effect in the former case ; 
whilst the eggs of animals appear still less tena- 
cious of vitality, although in a few instances 
capable of retaining it for some time, even under 
considerable disadvantages, as will be presently 
noticed. 
The seeds of most plants which inhabit tem- 
perate climates are adapted to remain dormant 
during the winter, and may be preserved in 
dry airand moderate temperature for a consi- 
derable time. Some of those which had been 
kept in the Herbarium of Tournefort for up- 
wards of a century were found to have pre- 
served their fertility. But with regard to those 
which are brought from tropical climates there 
is greater uncertainty, and unless they have 
been carefully excluded from the contact of air 
and from variations of temperature, a large pro- 
portion are usually unproductive. Cases are of 
no unfrequent occurrence in which ground that 
has been turned up spontaneously produces 
plants dissimilar to any in their neighbourhood. 
There is no doubt that in some of these the 
seed is conveyed by the wind, and becomes 
developed in spots .which afford congenial 
soil, in the same manner as the germs of 
fungi and infusoria. Thus itis commonly ob- 
served 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 ; and it is stated by Professor Graham 
that after any hill-pasture in Scotland has been 
laid dry and limed and the surface broken, 
white clover always makes its appearance. 
But there are many authentic facts which can 
only be explained on the supposition that the 
seeds of the newly-appearing plants have lain 
for a long period imbedded in the soil, at such 
a distance from the surface as to prevent the 
access of air and moisture, and that, retaining 
their vitality under these circumstances, they 
