

ELLSHA MITCHELL SCIENTIFIC SOCIETY. 121 



111 consequence of the presence of the bacteria-tube in the deep 

 layers of the rind the cells lying near begin to increase in num- 

 ber by division, slowly at first, but soon in rapid succession. At 

 the si me time the bacteria-tube grows into this newly formed 

 tissue and branches profusely. Following this division of cells 

 there arises at this point a meristeraatic or growing tissue which 

 through rapid increase becomes of considerable size, in which now 

 the characteristic tissue of the knot is differentiated. In the midst 

 of this meristematic tissue there arises a parenchymatous tissue, 

 of large cells, into which the bacteria-tube grows and branches 

 profusely in all directions. Later, through the dissolution of the 

 tube the bacteria are set free in the parenchymatous tissue, which 

 now becomes the so-called " bacteroid tissue.'' The outside of the 

 knot is differentiated into the rind, a few layers of cells wdth 

 little plasmic contents disposed radially, the outside layer of which 

 becomes corky. Between the bacteroid tissue and the rind is a 

 zone of small-celled tissue capable of division and growth and 

 free from bacteria, the meristem or growing point of the knot. 

 On the inner periphery of the meristem a zone of fibrovascular 

 bundles is formed, which originates as branches from the central 

 cylinder of the root. Between the fibrovascular zone and the 

 bacteroid tissue a layer of starch containing cells exists. As the 

 knot or tubercle enlarojes the meristematic zone bv p'rowth 

 advances in a peripheral plane. The peripheral part of the 

 parenchymatous or bacteroid tissue also continues to advance by 

 growth, and the peripheral part being younger contains the bac- 

 teria-tubes with their rod-like bacteria contents, and these bacte- 

 ria-tubes continue to grow and follow up the advancing periphe- 

 ral portion of newly formed parenchymatous tissue, while behind 

 follows up the process of dissolution of the membrane of the 

 tube and the liberation of the bacteria into the plasmic contents 

 of the cells making the bacteroid tissue. 



From several series of experiments conducted with every pre- 

 cautionary measure he reaches the conclusive proof that by means 

 of infection with knot-bacteria the plants (peas) even when 

 grown in a soil deprived of all nutriment and providing for the 



