90 MISSOURI BOTANICAL GARDEN. 





the forms under consideration it is rather difficult to deter- 

 mine how closely the fungus is related to the external en- 

 vironment. The host and fungal relationship may be - 

 slightly symbiotic from the fact that only a few cells are 

 infected, yet a large number of cells is produced by the 

 fungal stimulation, this excess of growth being easily noted 

 just at the region where internal infection takes place. No 

 hyperchromatic cells, so common in other tubercles, are pro- 

 duced in Myrica. As has been previously stated, the host 

 cells of the three forms studied are destroyed as a result of 

 their association with the fungus. In Myrica the problem 

 regarding the function of the fungus in the tubercle is still 

 unsolved. In Ceanothus and Elaeagnus, on the other hand, 

 the evidence that the fungus is digested in part by the host 

 cell indicates that the plant may derive some benefit from 

 the fungus. The statement is frequently met with that the 

 fungal organism in Elaeagnus enables the plant to utilize 

 the free nitrogen of the air. This must be based on an 

 analogy with the alder, for I have found no experimental 

 data of any investigator which will substantiate such an 

 assertion. 



Zach (55, 57) lays great stress upon the digestive activity 

 of the host cell in the several forms which he has studied, and 

 attributes to it functions similar to those of the phagocytes 

 found in animals. Even though the fungus is destroyed in 

 part by the cytoplasm of the cell, the above analogy does 

 not explain the actual processes which take place when the 

 fungus is destroyed. 



Regarding its systematic position, the fungus in the tuber- 

 cles of Ceanothus and Elaeagnus must be retained within 

 the genus Frankia, respectively as Frankia subtilis Brun- 

 chorst, and Frankia ceanothi Atkinson. The fungus found 

 in Myrica, as already pointed out, has but a few minor char- 

 acteristics in common with the species found in Ceanothus 

 and Elaeagnus, and should probably be placed in a separate 

 genus. The name Frankia Brunchorstii serves the purpose 

 of designating it only by a great extension of the generic 

 characters of Frankia, its Actinomyces nature making it 

 quite distinct from the other species. 



