FUNGI 159 
balls; but it is thought that a basidium is represented also 
in the life-history of the rusts, and hence they are now 
included among the Basidiomycetes. This supposed ba- 
sidium of the rust is the little filament produced by the 
winter spore, which sends out branches that bear the small 
early spring spores (§ 84). 
88. Mycorhiza.—This name means root-fungus, and 
refers to an association that exists between certain Fungi 
of the soil and the roots of higher plants. It was thought 
once that this association of fungus and root occurred only 
in connection with a limited number of higher plants, 
such, as orchids, oaks, heath plants, etc.; but more recent 
study indicates that probably the large majority of vascular 
plants, that is, plants with true roots, have developed this 
relation to a soil fungus, the water-plants being excepted. 
It has been found that the humus soil of forests is in large 
part “a living mass of innumerable filamentous Fungi.” 
It is of advantage to roots to relate 
themselves to this great network 
of filaments, which are already in 
the best relations for absorption; 
and those plants which are unable 
to do this are at a disadvantage in 
the competition for the nutrient 
materials of the forest soil. It is 
doubtful whether many vascular 
green plants can absorb from the 
soil enough for their needs with- 
out this assistance; and if this is 
true, the mycorhiza Fungi become 
Fie. 153.—Mycorhiza: the tip 2 L : . 
of a beech rootlet enmeshed of vital importance in the nutri- 
by a soil fungus.— After 
FRANK. : 
tion of such plants. The delicate 
branching filamentsof the mycelium 
either enwrap the rootlets witha jacket of interwoven threads 
(Fig. 153), or occur within the cortical cells of the root. 
