1902] BINUCLEATE CELLS IN HYMENOMYCETES 17 
of growth of the hyphae of the gills and give the largest per- 
centage of cells cut. longitudinally in the young gill. This is 
-of course. true for the young gills on one side of the carpophore 
only, those on the opposite side, as will be readily understood, 
showing the hyphal cells cut more nearly transversely than in 
exactly transverse sections of the entire carpophore. Fig. 17 
shows the section of a very young gill taken from such an 
oblique section of:a carpophore, The cells are nearly all cut 
longitudinally, and the method of their growth and _branch- 
ing is fairly-well indicated. Still even here certain hyphae are 
seen to have turned up or down and out of the plane of the sec- 
tion, so that the axial hyphae of the base of the gill and the 
end cells are not connected to form a continuous hypha in the 
section. 
The conspicuous fact here is that all the cells of the gill are 
binucleated. Following backward through the base of the gill, 
we should pass suddenly into tissue of the pileus exactly similar 
to that shown in the inner portion of fig. 73. It is not easy to 
trace a single hypha from the one tissue to the other; still there 
seems no doubt that the binucleated cells are the end ramifica- . 
tions of hyphae which farther back in the pileus and stipe are 
composed of multinucleated cells. In other words, as Maire’s 
work shows, the ends of the hyphae which are to reproduce the 
organism by means of basidia and basidiospores have maintained 
the binucleated condition, while the mass of the hyphal cells, 
having only the functions of support and transportation of 
water, etc., to the reproductive cells to provide for, have become 
enlarged and multinucleated as a result of nuclear divisions unac- 
companied by cell division. The reproductive series of cells, 
the Keimbahn of various authors, is thus sharply distinguished 
from the purely vegetative and somatic series by the number of 
nuclei which they contain respectively. In very early stages in 
the development of the carpophore the differentiation of the 
two types of cells is present and continues through its whole 
development. Whether the multinucleated cells increase in 
number by cell division, as do the binucleated, is not easy to 
