The First Land Plants 
gas nitrogen and sharing it with the nostoc.* In return 
the nostoc gives up some of its sugary material or 
other product of carbonic acid to the bacterium. 
The best way is to consider the two as friends (as 
one would understand this term in the City), that is, 
“business ” friends. . 
The whole group of fungi were very likely at one 
time green algee. Some of them, like the colourless alga, 
choreocolax, mentioned in the last chapter, found out 
a simpler and easier way of living as parasites, clinging 
to and devouring other algz. 
One might almost suggest that they trained them- 
selves by the destruction of many green alge until 
they became specialists and very expert in adsorbing 
food material. At any rate fungi and especially bac- 
teria are nowadays experts in the work of getting 
nitrogen and other salts from any kind of material, 
whether living or dead. 
Somehow or other the azotobacter or its ancestors 
discovered how to seize the nitrogen of the air and 
turn it into nitrates and nitrites, 
The two together, the nostoc and azotobacter, work 
as a co-operative company. They are now a mutual 
blessing ; both benefit from the association, but yet, 
like some business friends, they are apt to become 
parasites, and require to be carefully watched. 
After the discovery of azotobacter or nostoc, the 
mud of almost every ocean was searched for this 
interesting germ, and it has been found in Java, in East 
Africa, in Heligoland, and in the Baltic.t? Swarms of 
* Nitrogen, sulphur, carbon, coal, and peat are all oxidised by bacteria. 
How it is done, no one has explained. Nitrates are formed in the atmosphere 
by electric discharges (lightning flashes). Is it possible that bacteria produce 
it by electrical activity ? 
+ Bacteria occur in small numbers in sea-water, but not apparently below 
100 fathoms deep. 
44 
