Aimes and Elaeagnus. 12 7 
2. The tubercles are produced by the infection of the root with a species 
of the nitrogen-fixing organism Pseudomonas radicicola. 
3. The bacillus enters the root and afterwards propagates itself in the 
cortex of the nodule as a rod-shaped organism. In Elaeagnus it produces 
a very definite zoogloea. 
4. The further development of the organism, in both cases, gives rise to 
relatively large spherical bodies, which increase in numerical proportion until 
they fill the entire cell. 
5. Under certain conditions the larger bodies divide into two, and then 
each divides again, and possibly even further, until they lose their identity 
and a group of bacilli remain in their place. 
6. Pseudomonas radicicola is a polymorphic organism, the bacillus and 
coccus being different forms of one and the same organism. 
7. In Elaeagnus the nuclei of the host cells appear to undergo some 
change under the influence of the zoogloea. 
8. In Elaeagnus the Bacteria are found mainly in the region imme- 
diately behind the growing point, whilst in Alnus the bacteroidal tissue 
traverses the entire length of the nodule. 
9. In Elaeagnus the food storage cells are found towards the base 
of the tubercle, in Alnus there are zones of tissue concentric with the 
endodermis, and in both the endodermis performs this function. 
10. In Elaeagnus isolated groups of bacilli occur in the basal region. 
11. The coccus form appears to be correlated with scarcity of available 
carbohydrate and change of environment. It is much more resistant to the 
influence of external agencies than the rod-shaped form. 
12. The organism is capable of fixing free atmospheric nitrogen when 
isolated from the tubercles, and its presence is undoubtedly beneficial 
to the plant. 
Bibliography. . 
Bottomley, W. B. : The Cross-inoculation of the Nodule- forming Bacteria from Leguminous and 
Non-leguminous Plants. Report British Assoc., 1907. 
BjoRKENHEIM, C. G. : Beitrage zur Kenntnis des Pilzes in den Wurzelanschwellungen von Alnus 
incana. Zeitschr. f. Pflanzenkrankh., 1904. 
Brunchorst: Uber die Wurzelanschwellungen von Alnus und der Elaeagnaceen. Unters. a. d. 
bot. Inst. Tubingen, ii, 1886. 
Frank: Sind die Wurzelanschwellungen der Erie und Elaeagnaceen Pilzgallen? Berichte d. 
deutschen botan. Gesellsch., v, 1887. 
