62 
Plant and Animal Bacterial Disease Compared. 
Of recent years much more research work has been carried 
out in plant pathology, and many more plants have been found to 
suffer from diseases caused by minute fungi than were formerly 
dreamt of. The higher plants suffer most, and every flowering 
plant has one or more fungi which prey upon it. 
Massee estimates that the annual loss on cultivated plants 
due to fungi is at least ^2,000,000,000. The Prussian statistics 
bureau gives the loss on cereals from rust alone as 20,000,000. 
In the United States the loss on bitter rot in apples is 
estimated at ^2,500,000. 
Some of them act very quickly, and kill their host. Pyihiitm r 
the “ damping off ” of seeds causing death of the seedling in 
about four hours. “ Smut ” in the oat is present in the soil, 
affects the seedling, and the Mycelium or spawn grows with the 
seedling and lies dormant till the ear is formed, when, passing 
into the ear, it forms the black powdery mass, which prevents the 
proper formation of the cereal. 
The “ Smut,” or spore, is cast on the ground to await the 
next year’s seedling, when a similar infection takes place. 
Phytophthora infestans (potato disease) has summer and winter 
spores. You can notice a large black patch on the leaf of a 
potato, and around this the summer spores soon appear hke a 
white mildew, at the same time the spawn grows down the plant 
and enters the young potato, and there, forms a hibernating 
mycelium, scarcely recognisable in the potato, but always ready 
to form summer spores in the plant of the potato the following 
year. This fungus, finding that the market gardener distributes 
these young potatoes all over the world, has ceased to form winter 
spores at all, and depends on this hibernating spawn, a very 
curious instance of adaptation to surroundings. 
Another curious instance of adaptation to surroundings is 
that when some saprophytes or those that feed on dead material, 
are fed solely on the sap of plants, they can be educated through 
several generations to become parasitic, and ultimately to attack 
the new host plant without the assistance of artificial food stuff. 
Most plant parasitic fungi, just as we saw in animals, require 
an abrasion, or small wound, before they gain an entrance. 
The surroundings, similarly, must be suitable, in fact, the 
potato disease has been shown at Kew not to grow unless the 
surroundings are hot and damp. 
The host must be run down, over-watering being a common 
cause, and you must have the special fungus or microbe. 
It will be seen, then, that wood, leaves, and other organic 
dead matter, or a living plant which is in a depressed condition, 
are necessary for the existence of these microscopic fungi, and 
when, in the Autumn, a plant is weak, or vhen it is growing 
rapidly, as in the case of the seedling, are the dang'erous times, 
just as we have typhoid in the Autumn and tubercle in the young. 
