6 
Assimilation, independent growth, power of movement, 
respiration, and reproduction are the five chief functions, the 
possession of which separates both plants and animals from 
lifeless bodies. 
It is of life manifesting itself by function, whether as 
exhibited in a monocellular plant, or in an organism of a million 
differentiated cells, that I wish to address you, and also of life 
disordered and destroyed by over-function, or fatigue. 
It is this force which governs waste and repair, and carries 
out its work with marvellous accuracy. It has been estimated 
that about one twenty-fourth part of our body perishes day by 
day, and to repair the loss we consume about a ton of material 
every year. No part of the present audience existed a year 
ago except, perhaps, the teeth (especially if false); and yet so 
accurately has the new replaced the old that, had this audience 
been photographed a year ago, and again to- night, it would look 
the same, and individually would feel the same. 
The life of all organisms, whether plant or animal, is made 
up of alternating periods of activity and repose ; of function and 
of rest to prevent, or to repair, the effects of fatigue. There is 
no exception to this rule. The busiest man has to rest some- 
times, or suffer for his folly. The laziest cell must do some work 
or become atrophied and useless. Yes! and I venture to suggest 
that, to a certain extent, the same law holds good beyond the 
limits of the organic kingdom, and is found in the inorganic as 
well. The soil must lie fallow sometimes, or it becomes fatigued 
and less productive ; and the farmer must humour his fields by a 
rotation of crops, or the land becomes sulky and unresponsive, 
and the coming rent day will find him with a meagre balance at 
his bankers. 
Fatigue in some plants is prevented in a way that may strike 
you as rather remarkable. Mr. Ward in his book on “The 
Growth of Plants in Closely Glazed Cases” says: ‘‘ All plants 
require rest, and obtain it in some countries by the rigour of winter, 
in others by the scorching heat of summer. Collectors often fail 
in their attempts to grow certain plants from want of attention to 
this essential point. Thus most Alpine plants which enjoy an 
unbroken rest underneath the snow for several months are very 
difficult of culture in our own mild and variable winter. The 
winter of 1850-51 was ushered in by some heavy snows with 
which I filled my Alpine cases, giving the plants perfect rest for 
three or four months, and with a most satisfactory result, the 
Frimula Marginata, the Zzmnea Borealis, and other species flowering 
much finer than usual. Many of these plants would, I am con- 
vinced, succeed well if kept for five or six months in an ice house. 
Plants in hot countries have their periods of rest in the dry 
season. In Egypt the blue water lily obtains rest in a curious 
