FUNGOUS ROOT-TUBERCLES. 77 



or all pass out of the cell (f. 18). Apparently the fungus 



secretes some enzyme which dissolves the cellulose wall and 

 thus prepares the way for the infecting hyphae. Upon enter- 

 ing, the fungus directs its hyphae toward the nucleus, then 

 it builds up a dense tangled mass on one side, frequently 

 crowding the nucleus out of its original position. In many 

 of the infected cells the nucleus lies close to the cell wall and 

 the fungal mycelium nearly fills the remaining space. Figure 

 19 shows where such a condition is just beginning. Again, 

 other stages are found where the nucleus has retained the cen- 

 tral position in the cell and the fungus builds its structure 



entirely about it (f. 16, 19). 



When the fungus enters a cell the first noticeable fea- 

 ture is the increase in size of the nucleus, then follow the 

 growth of the cell wall, the disappearance of the grains of 

 starch and the formation of dense cytoplasmic masses in va- 

 rious parts of the cell. The latter may be comparable to that 

 substance in the host cell which Zach (58) calls the "Ex- 

 kretkorperchen." No indications are found in any of the 

 Elaeagnus material examined that large portions of inter- 

 cellular walls are dissolved in order that a larger space may 

 be provided for the fungus; a phenomenon invariably found 

 in the tubercles of Ceanothus. In Elaeagnus the cell walls 



may 



more 



break down the walls of the host cell. The normal cells ad- 

 jacent to the infected ones show no signs of being affected in 

 any way by their neighbors at least as far as cell content is 



concerned. 



With the increase in size of the cell and its nucleus, the 



nucleo-cytoplasmic relationship is constantly 



main 



measurements 



measurements 



accurate as possible indicate that a definite ratio exists between 

 the size of the nucleus and that of the cell. All nuclei of the 

 infected cells, which at first are spherical often containing 

 several nuclei, are in the so-called resting stage, the chromatin 

 being distributed in very fine masses ; frequently this is very 



dense 



The 



