PLANT COMPANIONSHIP IN THE FOREST, 173
well is essential to the process. In the presence of glucose—the sugar pre-
sent in the cells of the tubercles—the Nitro-bacteria or bacteroids seem to
have the power to assimilate free nitrogen from the air in the soil, and the
plant appears to consume these bacteroids with their contained resultant
nitrates ; whilst, as the tubercles become disorganised, the released bacteroids
infect other roots. Though our knowledge of the whole process is as yet far
Fig, 4. Portion of clover root show-
ing (0 tubercles and (l) root-branches.
Fig. 5. Fragment of tissue from
tubercle of root of clover (magnified)
(a) peripheral cells ; (b) infected cells,
strongly nucleated.
Fig. 6. One of the infected cells (a)
from the root-tubercle of clover ; n.,
nucleus ; v., vacuole ; b., bacteroids ;
B., ordinary cells (much magnified)'
Fig. 7. Isolated bacteroids. a., from
younger tubercles; b., from older tuber-
cles (much magnified).
from complete, it is obviously one of primary importance to agriculture,
indicating as it does one of the most valuable functions of leguminous crops ;
and at the same time it would be difficult to find a more interesting example
of the mutual dependence of plant lives.
[For the loan of the figures illustrating this Address the Club is indebted
to the courtesy of the Editor of The Journal of the Essex Technical
Laboratories.]