92 TOBACCO LEAF. 



parent cell of a little, bubble-like offshoot; this, when 

 sufficiently developed, detaches from the parent and 

 assumes an independent existence. 



Most important of all is that class of ferments 

 known in general as bacteria. There are many spe- 

 cies of these, differing in shape, mode of aggregation, 

 conditions of life and products. If a liquid containing 

 bacteria be examined, it will often be found swarming 

 with these little organisms, ranging from ^^ to less 

 than ^isiT of an inch in size, according to the species. 

 The little beings are not quiet, but are vigorously active. 



Eeproduction of the various species is accomplished 

 in two ways : First, by fission, or the splitting in half 

 of the single-celled parent ; the small halves then sepa- 

 rate and grow to full size. Second, many species develop 

 within the body of the parent a number of thick-walled 

 bodies, or spores, which are later discharged, and which, 

 under favoring conditions, develop into the normal, ma- 

 ture bacterium. 



Most important features of these organisms are 

 their wide distribution and their wonderfully rapid mul- 

 tiplication. Though requiring a certain amount of 

 moisture for their active life, they are not destroyed by 

 slow drying at a low temperature. In consequence, they 

 are carried as dust by every passing wind, to new lodg- 

 ing places, where they develop if the conditions are 

 favorable. As, under most favorable conditions, the 

 individuals of some species can reproduce in twenty 

 minutes after their own birth, it is a simple arithmetical 

 process to show that a very short time would suffice for 

 them to occupy the globe. Such favorable conditions 

 never occur; but the multiplication often observed is, 

 nevertheless, tremendous ; and the fermentative changes 

 produced are correspondingly great. 



The conditions surrounding them greatly influence 

 their activity and multiplication. Some require free 



