SIDE LIGHTS ON THE POTATO DISEASE. 
161 
may be termed privileged spores, which mature within them- 
selves (by a differentiation of their contents) certain repro- 
ductive ciliated bodies called zoospores. When these zoospores 
are ripe and set free, they move about in moisture by means 
of two cilia with great rapidity, and either work their way 
into the breathing pores or germinate at once on the leaf 
surface, and penetrate the cuticle like the ordinary spores. In 
the wet dewy mornings of early autumn, when all the leaves are 
moist, it will be seen that a few infected plants may be the means 
of rapidly diffusing the disease (by means of these ciliated 
zoospores alone) over a very large expanse of cultivated ground. 
Now if we could imagine the whole of Britain free from the 
disease and a single infected field somewhere in France or 
Germany, a single puff of wind would send the spores over to 
us, and we should at once be as badly off as if we had suffered 
from the disease from the first. 
As the murrain never comes upon us till a certain time in the 
early autumn, the most reasonable suggestion for exterminating 
the disease seems to be to cultivate those early varieties of 
potato which mature their fruit before the fungus makes its 
attack, and so evade the disease ; but it will be seen singularly 
enough, from our actual experiments, that it was a positively 
late potato, and not an early one , which entirely warded off the 
murrain, whilst the earlier varieties succumbed. And so we 
leave the subject. We can state facts, and call the facts by 
names ; but as to what the disease is, we can say little more 
than that the potato disease is the potato disease, as cholera is 
cholera. 
VOL. XIII. — NO. LI. 
M 
