I 



96 





MISSOURI BOTANICAL GARDEN 



tub 



that.it is not present in the normal root. 



The question still presents itself whether the enzyme is 



oduced 



host 



fungu 



from 



cell produces an enzyme. The dissolving of the 

 cell walls in the tubercles of Ceanothus presents a fact which 



that 



Thus 



there may be two enzymes present, one produced by the host 

 cell and another by the fungus, for it is hardly probable 

 that the host cell forms an enzyme which dissolves its own 

 walls. Until a sufficient amount of pure culture of the 

 fungus can be grown, it is impossible to decide whether the 



secretes an enzyme or not, but the conditions are 

 probably quite similar to those which Marshall Ward found 

 in Botrytis, which produces cytase capable of dissolving the 

 walls of the host cell. 



gus 



SUMMARY OF RESULTS. 



The Tubercles of Ceanothus. 

 1. Judging from the common occurrence of the tubercles, the infec- 



fungu 



2. External in- 



fection probably takes place through a root hair or an epidermal cell 

 from which the subsequent tubercle is formed. 3. The tubercle con- 



sys*e 



layer; the 



sporanges 



inner, the vascular cylinder; and the middle or cortex, which contains 

 the infected cells. 4. Internal infection occurs in the growing region 

 and takes place by the fungus passing from cell to cell. 5. Three 

 distinct stages of fungal development may be noted: the mycelia 

 stage found in the host cell; the stage with the 

 initiates the conditions for the digestive cell; and~ the last stage, 

 where all but the walls of the mycelium are absorbed. 6. Because of 

 infection, hypertrophied cells and nuclei are formed. The fungus 

 dissolves the walls of the host cell. 7. The host nucleus increases in 

 volume; with it, there is an increase of the nucleole and in the 

 amount of chromatin. 8. Following the vesicular stage the cytoplasm 

 and nucleus of the host cell are absorbed. Subse< 



ngus 



;o this, the 

 9. Both the host cell and the 



fungus finally die and undissolved portions of the fungu 



the cell. 10. Symbiosis exists, which is quite apparent in the early 

 stage. 





