1 98 
Sprcitt . — A Comparative Account of the 
(b) In Genista the primary vascular strand is diarch and 
the tissue between the bacteroidal zones is all paren- 
chyma. 
II. The Phaseoleae and Trifoleae type, in which the bacteroidal 
tissue always remains an undivided central zone, the growing 
point becomes localized apically, and zoogleal threads are 
prominent in the young nodules. 
(a) In Phaseolus the basal vascular strand divides into 
four. 
(b) In Ononis the basal vascular strand divides into two. 
(c) In Trifolium the single strand remains undivided for 
some time. 
III. The Viceae type, in which there is a well-defined apical meri- 
stem with a basal intercalary zone. Zoogleal infection threads 
are very prominent. Two vascular strands have a separate 
attachment to the root-stele. 
IV. The Mimosoideae type, in which the nodules persist for more 
than one year. 
6. When the zooglea persists and envelops the nuclei, the latter 
become vacuolate, then amoeboid, and later divide amitotically. 
7. After the disappearance of the infection threads the bacteria assume 
a variety of forms known as bacteroids. 
8. The production of slime is connected with the amount of nitrogen 
fixed, and is influenced by the medium in which the bacteria are living. 
9. The nature of the cell-sap has a marked influence on the capabilities 
of the bacteria. 
10. The form of the nodule depends primarily on the nature of the 
environment of the host, which influences the cell-sap and consequently 
the behaviour of the bacteria after they have entered, and secondarily 
on the anatomical peculiarities of the particular plant. 
Bibliography. 
BeijeRINCK, M. W. : Die Bakterien der Papilionaceenknollchen. Bot. Zeit, vol. xlvi, 1888. 
Bottomley, W. B. : The Cross-inoculation of the Nodule-forming Bacteria from Leguminous and 
Non-leguminous Plants. Report Brit. Assoc., 1907. 
— : The Root-nodules o i My rica Gale. Ann. Bot., vol. xxvi, 1912. 
Brunchorst, J. : Ueber die Knollchen an den Leguminosenwurzeln. Ber. d. Deutsch. Bot. Ges., 
vol. iii, 1885. 
Buchanan, R. E. : The Gum produced by Bacillus radicicola. Centralbl. f. Bakt., Abt. ii, 
Bd. xxii, 1909. 
