Notes. 
607 
described, it might be said that this takes place along an asymptotic 
curve, continually approaching but never becoming equal to zero. 
According to the other, protoplasm passes absolutely from the 
kinetic to the static condition. Its locked-up energy becomes purely 
potential, and Professor C. de Candolle has not hesitated under these 
circumstances to compare it to an explosive. 
It has been pointed out that such a conclusion is absolutely in 
conflict with Mr. Herbert Spencer’s well-known definition of life. 
But it appears to me that that definition was only intended to apply 
to higher stages of the aggregation of living matter than that of the 
physiological molecule on which I have endeavoured to fix the 
discussion. The question seems to me to be simply whether it is 
admissible to regard that as capable of being brought to an absolutely 
static condition. 
Conceive two such molecules, one known to be living, but static, 
and the other dead, and both to be maintained in a condition in 
which they are not immediately susceptible to chemical change. 
What is the criterion of life ? There is none. It seems to me then 
that the question I have propounded does not admit of any positive 
answer in the present state of our knowledge. 
A problem, perhaps somewhat scholastic, which once vexed the 
souls of biologists was — whether life was the cause of organization 
or organization of life. What is to be our answer if our starting- 
point is no more than a possible ‘ explosive ’ ? 
ON THE STRUCTURE OF THE STEM OF A RIBBED 
SIGILLARIA l . By Professor C. E. Bertrand. — The structure of 
certain species of Lepidodendron , e. g. L . selaginoides and L . Har- 
courtii , is well known, and we are in possession of some facts as 
to the anatomy of Sigillaria spinulosa and S. Menardi, species which 
belong to the section of the genus characterized by a smooth bark 
{Leioder maria). On the other hand, we are still in want of data 
with regard to the structure of the Rhytidolepis section of Sigillaria — 
the species with a ribbed bark. It has been suggested that some 
of the stems described under the name Diploxylon may very probably 
be partially decorticated Sigillarias. 
In March of this year (1899) I received from the colliery of 
1 Abstract (translated) of a paper read before the Botanical Section of the British 
Association, Dover, Sept. 1899. 
