1902] BINUCLEATE CELLS IN HYMENOMYCETES 7 
interchange of food materials, etc. Such a fusion is shown 
in fig. zo, in the lower right-hand part of the subhymenial tissue. 
The mycelium of Hypochnus in the case studied forms no 
felt of hyphae on the surface of the substratum, apparently, 
until the time has arrived for the formation of basidia. That 
is, through its purely vegetative existence it is entirely buried. 
When the hymenium is to be formed, erect aerial branches are 
pushed up, and branch into the tufts referred to above as figured 
by De Bary. The main axes of these tufts are never close 
packed, but arise from the substratum at relatively considerable 
distances from eachother. Their abundant interlacing branches, 
however, form a dense hymenial layer higher up. We have 
thus a condition in this respect resembling a diminutive forest, 
or growth of shrubbery, whose branches and twigs are densely 
interlaced, while the trunks from which they arise are separated 
by relatively wide open intervals. This is shown, with a modi- 
fication noted below, in the semi-diagrammatic fig. zo. The whole 
mass of the hymenium here shown is supported by the three 
hyphae arising from the substratum. The figure, to be sure, is 
of a section, so that part of the hymenial cells belong really to 
other twig systems arising above or below the level of the sec- 
tion. A corresponding portion of the branches of the two main 
hyphae figured lie also above or below the section, and hence 
do not appear, so that the proportion of peripheral branches to 
main axes as shown is not materially affected. The case is 
further complicated frequently by proliferation from the surface 
of an old and apparently exhausted hymenial layer. This is the 
condition shown in the figure in question, where the hymenium 
which shows the immature basidia has been superimposed on 
the surface of an older one. The upper surface of the latter is 
very clearly indicated, and it is at once seen that the same 
method has been employed in forming the second hymenial 
layer as in the first case. The old hymenium has become the 
substratum out of which arise scattering vertical hyphae, which 
by their copious branching then form the new hymenium. The 
old hymenium is seen to consist of a mass of hyphal cells very 
