CHAPTER VI 
DISEASES DUE TO BACTERIA 
ANOTHER class of micro-organisms which cause plant 
diseases are the bacteria. Plant bacteria are generally 
rod-like in form (Fig. 35), varying from one thirty- 
thousandth to one ten-thousandth part of an inch in 
length, and about a third of that in diameter. They 
multiply by dividing across the middle, each half 
becoming a separate bacterium. 
This process takes place so fre- gts 
quently that in a short time 
many millions of bacteria are pr See by: 
produced from one original 
parent. Certain bacteria may 
divide once every’ twenty 
minutes, and at this rate the 
progeny of one bacterium 
would exceed sixty-four thou- 
sand million in twelve hours, 
were all the ofispring to Fie. 35. Typical appearance of 
remain alive. Most disease- bacteria pathogenic to plants. 
producing bacteria possess a number of tiny “ tails” or 
flagella, by means of which they are able to swim in water. 
Some types of bacteria produce within their bodies 
hard, resting spores, capable of withstanding abnormal 
conditions, but bacteria causing diseases of plants are 
not known to do this. 
Bacteria are carried from plant to plant by wind, 
rain, insects, and animals, including man. Once on the 
plant they may enter the inner tissues by means of the 
stomata, or by wounds, and in this process they are 
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