ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
639 
solutions, &c. Under these circumstances, the protoplasm which has 
hitherto been spread throughout the cell and lined quite completely the 
cell-wall, becomes contracted, assuming various shapes and positions. 
Several examples of this inspissated condition of cell-plasma are 
depicted in his illustrations ; such are the appearance of the cholera 
nostras bacillus, typhoid bacillus, Bacterium termo, Clostridium buty- 
ricum , Bacillus neapolitanus , Leptothrix buccalis , and Spirogyra. In the 
bacilli, the plasma, acted on by salt-solution, is gathered up as polar 
bodies at one or both ends of the cell ; if at both, then the polar bodies 
may be joined by a narrow tilament of inspissated plasma. 
Quite similar effects, but with different arrangement of the plasmo- 
lysed cell-contents, are easily seen in Spirogyra. The plasmolytic 
condition is easily induced by any substance which will withdraw water 
from the cell-protoplasm, but the most convenient medium appears to 
be sodium chloride in solutions of 1/2 to 10 per cent., 1/2 to 2 per cent, 
being the strength most usually adopted. 
Plasmolysis also occurs in disease conditions, and in cultivations ; 
examples of the former case are Streptothrix disease of rabbits, and 
actinomycosis. 
The condition of plasmolysis artificially induced by means of 
reagents is not without its practical value, for it enables the observer to 
determine whether the cells be still alive, viable indeed, since only 
living protoplasm is susceptible of this change. 
The author concludes by discussing the views of Ernst and Biitschli 
on the nature of protoplasm and the nucleus of cells in particular. 
Symbiosis of Rhizobium and Leguminosse.* — In an exhaustive 
treatise, Herr B. Frank sums up the present state of our knowledge 
of this subject, and adds some new observations. 
The symbiotic organism he regards as a Schizomycete, Bhizobium 
Leguminosarum, common to all the Leguminosae. He has isolated and 
cultivated it in hanging drops. In a period varying from 1 to 5 days 
there appear in the drop actively motile swarmers which originate from 
the bacteroids in the tubercle. The coccus-like contents of these 
bacteroids develope into the swarmers which become free and motile 
after the absorption of the bacteroids. They are of roundish form, from 
0*9 to 1*3 p in diameter, while the bacteroids are from 3 to 5 * 5 p long, 
the microbes lying in the latter usually in one row. Non-motile 
bacteria also occur. No cilia could be detected. A zoogloea-f'orm was 
also observed. The bacteroids are therefore neither purely proto- 
plasmic structures (Brunchorst) nor pure bacteria (Prazmowski), but 
a combination of the two, a mycoplasm. The author regards the microbe 
to be a parasite in Phaseolus, and the formation of tubercles to be of no 
use to the host. In most other Leguminosae, on the contrary, the 
relationship of the microbe to the host is a symbiotic one, enabling the 
latter to obtain normal development under unfavourable conditions of 
growth, in soil containing but little humus. He finds the Bhizobium 
not only in the root-tubercles, but also in the aerial organs of the 
infected plants. 
* Landwirthsch. Jahrb., xix. pp. 523 et seq. (12 pis.). See Bot. Centralbl., xlv. 
(1891) p. 242. Cf. this Journal, 1890, p. 372. 
