ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
357 
becoming protective organs, and losing their property of storing up 
reserve food-materials. 
Tubercles on the Roots of Leguminous Plants.* — Prof. H. M. 
Ward draws attention to some results of further investigation into this 
subject. In some of the cultures made in the summer of 1888, the roots 
of the pea were infected with bacteroids from the tubercles of the bean, 
and this is a point of some importance in view of the belief that each 
species of Leguminos8B may have its own species of bacteroid. Extracts 
of the tubercles containing infected germs were made ; and although the 
latter were taken from the tubercles of the bean, they infected the root- 
hairs of both peas and beans equally well. It is especially the young 
root-hairs, with extremely delicate cell-walls, that are infected, and the 
first sign is the appearance of a very brilliant colourless spot in the sub- 
stance of the cell-wall ; sometimes this spot is common to two cell-walls 
of root-hairs in contact, and not unfrequently several root-hairs are 
found all fastened together at the common point of infection. This 
highly refringent spot is obviously the “ bright spot ” referred to in a 
previous paper as the point of infection from which the infecting fila- 
ment takes origin. It soon grows larger and developes a long tubular 
process, which grows down inside the root-hair and invades the cortex, 
passing from cell to cell. The “ bright spot ” is, therefore, the point of 
origin of the infecting filament, and, as a matter of inference from the 
experiments, it cannot but be developed from one of the “ bacteroids ” 
or “ gemmules ” of the tubercles. 
The author then describes a series of water-cultures of beans infected 
artificially by placing the contents of tubercles on their root-hairs. 
These experiments have led the author to conclude that the organism 
which induces the development of the tubercles is so closely adapted to 
its conditions that comparatively slight disturbances of the conditions 
of symbiosis affect its well-being. It is so dependent on the roots of 
the Leguminosffi that anything which affects their well-being affects it 
also. 
Some experiments with peas were also made as to the alleged con- 
nection between the development of the tubercles and the increase of 
nitrogen in leguminous plants, the evidence all going to show that the 
leguminous plant gains nitrogen by absorbing the nitrogenous substance 
of the bacteroids from the tubercles. 
The author then compares the conclusion arrived at by Prazmowski f 
with his own. As to the occurrence, origin, and structure of the 
tubercles, they are in accordance ; but there is one point of difference of 
extreme importance between Beyerinck and Prazmowski on the one 
hand, and the author on the other hand, and that is on the subject of 
the cultivation of the “bacterium” in nutritive media outside the host- 
plant — or rather the other symbiont. 
Use of Anatomical Characters in the Classification of Plants.! — 
M. J. Vesque gives a number of examples of the use of anatomical and 
* Proc. Roy. Soc., xlvi. (1889) pp. 431-3 (1 fig.). Cf. this Journal, 1888, p. 251. 
t Cf. this Journal, ante, p. 59. 
X Bull. Soc. Bot. France, xxxvi. (1889) Actes du Congr^ de Bot., pp, xli.- 
Ixxvii. (5 figs ). 
