8 
Life and its Basis . 
[January, 
But I wish to observe here that conditions necessary to 
life are not the causes of it. The human mind has the power 
of constructing and putting together the various parts of a 
machine, and of imposing the conditions of its aCtion, and it 
is that mind that is the cause of its adting in any particular 
way. Just so are the “ presence ” and agency of mind abso- 
lutely requisite to initiate and continue the motions which, 
as far as physical evidence goes, constitute vegetable life.* 
It is not necessary for my present purpose to enter further 
into the mysterious arcuna of vegetable embryology. The 
same principle of life, whatever it be, undoubtedly presides 
over all the multifarious functions and processes of vegetable 
organisation. Its progress is a succession of alternations of 
life and death ; first of the material particles which compose 
the organism, and then the death of the whole organism. It is 
a perpetual entry and departure of the atoms of the “ anor- 
gana ” into the substance of the organism ; and, as life is 
the continuance of this aCtion, so death is its cessation, in 
any molecule, or organ, or individual plant. With regard 
to one of the main conditions of vitality, viz., certain degrees 
of temperature, it is only by observation and experiment that 
we can know the range of heat which is compatible with the 
continuance of life in any particular case. In a large ma- 
jority of instances it appears to be very limited; but it is 
difficult to imagine any physical necessity for the appoint- 
ment. All we can say is, that so it is. It has been particu- 
larly observed apropos of the experiments made by the late 
Mr. Crosse, which were at the time thought by many phy- 
sicists to prove the theory of spontaneous generation, that 
though it was assumed that the heat of boiling water had 
which his infusions were subjected must necessarily have 
destroyed every living germ, yet the fa<5t of the reappearance 
even when air was excluded, of amoeboid forms of life, rather 
went to prove that their germs were capable of passing 
through such a temperature without losing their vitality. 
On the other hand, we do not know what degree of cold a seed 
when quite dry will bear without its germinating power 
being destroyed ; or, more corredtly, what limits are actually 
set to their restoration to the vital state in regard to the 
temperature to which they may be exposed. 
But a question here suggests itself, which I have no reason 
to blink, viz., whether some of the vital phenomena of plants 
do not indicate the presence of a power of choice and selec- 
tion in the individual organism itself exerted for its own 
* See Sir J. Herschel’s Popular kettures, p. 458, 
