348 Ward . — Recent Publications bearing on the 
the assimilation of nitrogen by them, the so-called tubercles 
and the micro-organisms which dwell in them stand in the 
closest active connection.’ .... 
The following remarks may be made respecting this paper. 
It is above all unfortunate that the authors do not give 
us more details as to the analysis of their crops : in the 
absence of exact numbers, their conclusions as to the in- 
crement of nitrogen can scarcely be criticised. It must also 
be pointed out that the tubercles referred to do not contain 
bacteria, but that the ‘bacteroid’ bodies are minute yeast- 
like gemmules budded off from the hyphae of a true fungus 
which enters the root-hairs, crosses the cortex, and branches 
&c. in the tubercles. 
Before making any further observations, I may quote the 
following. 
In August 1886, a paper was published by Frank, on the 
sources of nitrogen of plants 1 , in which the author points 
out that Schultz-Lupitz and others have shown that Legu- 
minosae will grow for years, without any marked decrease 
in productiveness, on a soil which is barren, provided all 
other needful salts are supplied except the nitrogenous ones ; 
also that crops of Leguminosae preceding Gramineae on 
a given piece of land, enrich the latter in nitrogen. He then 
points out that three kilos per hectare is the most that could 
be supplied annually from the combined nitrogen washed 
down by rain from the air, whereas a normal yield cor- 
responds to about fifty-one kilos of nitrogen per hectare. 
In experiments with finely sifted soil consisting of sand 
and humus, the following results were obtained. A quantity 
of the soil was analysed : a second lot was put in vessels, 
and seeds of leguminous plants sown in them ; a third lot 
was allowed to stand in pots alone. 
All were exposed to the air, and watered with distilled 
water, and protected against insects. In the control-pots, 
all weeds were carefully removed as they sprang up. 
1 Ueber die Quellen der Stickstoff-nahrung der Pflanzen, Ber. d. deutsch. bot. 
Gesellsch., 1885, p. 293. 
