314 
Nature and Cause of the Potato Disease. 
single seed, whose diameter may be the one millionth of an inch, 
has generated countless numbers of bodies like itself, all of which 
possess the same fruitfulness, and prepared in their turn to gene- 
rate others also. Seed upon seed, and branch upon branch, are 
thus formed with a rapidity that sets at nought all computation, 
and bewilders the mind by its extent and complexity. Let a plant 
therefore become infested with the botritis, and what will be the 
effect? The answer to this is apparent. The vessels of a plant 
are what veins and arteries are to an animal — the channels of 
circulation ; and if these be gradually choked up, circulation is 
impeded, and vitality lessened ; and if the cause continue until 
circulation is suspended altogether, vitality ceases, and the plant 
dies. Such would be the fate of a plant infested with the botritis, 
for it has within itself an enemy that cannot be shaken off ; for it 
circulates with its juices, feeds upon its organs, chokes its 
channels, and destroys its vitality. 
I had four geraniums and a fuchsia cut down by exposure to 
several frosts in February and March. These were placed in a 
warmer atmosphere, and in the course of some weeks I observed 
an efflorescence on the mould. This efflorescence was principally 
white, mingled with a few patches of yellow and brown. On my 
first observing it, I supposed it to be some salt of lime, probably 
carbonate, and thought at the time no more of the subject ; but 
finding subsequently that some of the plants were apparently 
dead, and the efflorescence increasing, I examined it, and found it 
to have in every respect the character of the seeds of the botritis. 
I examined more minutely, after this discovery, into the nature of 
other similar efflorescences, and I found the same character in 
many of them : they were clearly the seeds of the botritis. One 
of the geranium pots contained the efflorescence so abundantly 
that 1 could have filled the cuticle of an ordinary pea with it. 
This equals a globule two lines in diameter : there must therefore 
have been on the surface of the mould of that one pot 1600 
billions of the seed of this fungus. But what is this number 
compared with what must be in existence ? If in a single flower- 
pot, some 7 inches in diameter, we find a number so great as far 
exceeds our imagination of it, what, I ask, must be the total of 
these existences in the whole world ? The mind is overwhelmed 
by the thought, for we cannot comprehend it. Great as the 
powers of the human mind undoubtedly are, here is a subject so 
minute in size, yet so abundant in numbers, as to elude its grasp. 
It laughs at figures, and defies their application to solve the 
problem. 
The seed of this fungus we find in the earth, so that we have 
no occasion to bring to our aid any extraordinary agencies for its 
propagation. Wc require neither wind, birds, nor any other 
