359 
and its Mycorhiza 
same Hold for hosts which have no chlorophyll ? Now Acton 1 
has shown that certain carbohydrates and bodies like carbo- 
hydrates, including extract of humus, can be absorbed by 
roots of ordinary green flowering-plants and assimilated. 
Combining Acton’s results with those of Boehm and Meyer, 
we assume that this assimilation is absolutely independent of 
light or chlorophyll. So it is a priori probable that flowering- 
plants devoid of chlorophyll can also utilize such organic 
compounds to supply themselves with carbohydrates, and 
in particular to build up starch. In this paper I show that 
the Fungus in the holosaprophytic Thismia , in fact, does derive 
its carbohydrate, largely and possibly entirely, from its host. 
Altogether there is much to indicate the probability that in 
all cases of symbiosis between a Fungus (including Bacteria) 
and another plant, the Fungus receives carbohydrates from its 
symbiont. 
Again, we know that Fungi (including Bacteria) can readily 
utilize unoxidized or feebly oxidized compounds of nitrogen 
(NH 3 , HN0 2 ) and sulphur (H 2 S0 3 , H 2 S 2 0 3 ), which are less 
easily, or not at all, assimilable by green plants ; and on the 
other hand that Fungi wholly or partially lack the power of 
employing nitrates, or to less degree sulphates, as food. In 
the cases of symbiosis of Bacteria and Algae, and in the 
leguminous tubercles, there is, despite of Frank’s researches, 
sufficient reason for the belief that the fixation of free nitrogen 
does not take place in the absence of the Bacterium or Fungus. 
This fact, together with the sudden increase of assimilation of 
nitrogen as shown in Thismia , suggests that in symbiosis the 
Fungus always absorbs, for the benefit of the community, 
unoxidized or feebly oxidized nitrogenous bodies which are 
not easily worked up by the host. This would explain the 
utility of mycorhiza to plants growing in the shade of the 
forest or devoid of chlorophyll, and with their absorbing 
organs dipping in humus. Fresh humous bodies are charac- 
terized by their poverty in nitrogen of any sort ; and what is 
1 Acton, The Assimilation of Carbon by Green Plants from certain Organic 
Compounds: Proc. Roy. Soc., vol. xlvi, p. 118, 1889. 
