GENERAL CONSIDERATIONS. 



ON THE SUPPOSED NORMAL OCCURRENCE OF BACTERIA IN PLANTS. 



We now believe that bacteria do not occur normally in the interior of sound plants. 

 The case is quite different, however, with wounded plants or wilted ones. Frequently sapro- 

 phytic bacteria have been found in such plants and occasionally mistaken for parasites. 



When bacteria are found in the tissues of plants in any great number we may assume 

 that they are disturbing elements, and that if they continue to multiply the result to 



the host or some portion of it must be some considerable diminu- 

 tion of vitality, even if no specific disease supervenes. Compen- 

 sations due to symbiosis are not here under consideration. 



The former great uncertainty as to the life-history and habitat 

 of bacteria led to many speculations respecting their normal occur- 

 rence in the interior of both plants and animals. The belief that 

 they might occur normally in the interior of plants arose from the 

 inexact observations and experiments of various early workers, 

 notably Bechamp and Hallier. The dispute continued for a number 

 of years but was finally settled in the negative. 



Bechamp went so far as to maintain that his microzymes were 

 always present in plants and animals, were in fact the simplest 

 components of the tissues and led an independent life after their 

 death and disintegration. Hallier believed that the protoplasmic 

 granules of fungi were converted into bacteria capable of an inde- 

 pendent existence.* Fremy maintained the existence of hemi- 

 organized bodies in the juice of fermentable substances which 

 bodies were converted into yeasts. Trecul believed in similar 

 transformations: granules of organic matter became motile bac- 

 teria. In a later time it was still believed by some that bacteria 

 could be cultivated out of the sound interior of plants and animals 

 and were normally present therein, and by others that they arose 

 spontaneously in all sorts of organic substances. That the organic 

 must have developed from the inorganic during some period in the 

 history of the earth seems probable, but we must look elsewhere 

 than to Bechamp and Hallier for evidence. 



The amount of ignorance and credulity respecting micro- 

 organisms prevalent in the middle of the last century seems aston- 

 ishing in the light of our present knowledge. It is, however, the history of all subjects 

 hedged about by difficulties. The beginnings are always foggy. 



Pasteur appears to have been the first to show that the sound interior of plants is free 

 from micro-organisms. He experimented on grape-berries, taking some of the juice from 

 the interior under such conditions as to preclude the entrance of surface bacteria and 

 placing it in sterile must which remained sterile, while flasks treated to the washings from 

 the surface of the grapes invariably developed growths of some sort. 



In 1 879-1 880, Chamberland working in Pasteur's laboratory showed that beans taken 

 directly from the interior of their pods were free from bacteria, i. e., did not contaminate 

 culture-media when put into them (see fig. 2). 



*Even in very recent times we have similar views occasionally coming into print, c, g., Dunbar's Zur Frage der 

 Stellung der Bakterien, Hefen und Schimmelpilze im System (1907), in which it is maintained that bacteria, yeasts 

 and fungi, are the product of algal cells. 



fFio. 2. Peas taken from pods less than 18 hours after picking and placed on sterile nutrient gelatin where 

 they have sprouted and grown entirely free from the presence of bacteria. Photographed Oct. 3, 1908, from sample 

 tubes sent the writer by Mrs. A. W. Bitting. Two-thirds natural size. 



23 



Fig. 2.f 



