in the Hymenomycetes. 497 
disappears, and the nuclear network of the one nucleus be- 
comes intermingled with that of the others, An oval-shaped 
nucleus is thus produced, in which the two nucleoli of its 
component nuclei can be distinctly seen (Fig. 5). The two 
nucleoli remain distinct for some time, but eventually they 
approach each other, come into contact, and finally fuse into 
a slightly elongate nucleolus which at last becomes perfectly 
spherical (Figs. 6 and 34). We have then a complete and 
regular fusion of all the parts of the two nuclei, resulting in 
the formation of a single large nucleus in the basidium. The 
basidium now increases largely in size, together with the 
nucleus. The nucleus takes up a position in the upper ex- 
panded portion of the basidium, and is found to occupy at 
least two-thirds of the diameter of the latter. 
It is at this stage that the structure of the nucleus can be 
most easily made out (Figs. 6 and 34). It consists of a nuclear 
membrane, nuclear network, and a large nucleolus. The nucleus 
is very distinctly defined by the nuclear membrane, and stands 
out boldly in the protoplasm, especially in A . stercorarius. The 
nuclear network is made up of a thread or threads, which are 
coiled into a somewhat loose knot. Rosen 1 finds that the 
network in the species examined by him consists of a single 
much coiled thread. The thread consists of a matrix, staining 
light blue, in which are embedded numerous granules of 
chromatin. The latter are placed at nearly regular intervals 
along the thread, and stain deep blue. The nuclear sap 
between the threads is unstainable. 
The nucleolus is very large, and stains deep bluish red : it is 
by far the most conspicuous object in the basidium, and has been 
often mistaken, doubtless, by earlier observers for the nucleus 
itself. It consists generally of a homogeneous mass, but often 
exhibits a vesicular structure, and occasionally is so full of 
small, clear spaces, like vacuoles, as to give it almost the 
appearance of a coarse network. Sometimes the nucleolus 
appears to be lodged in a distinct cavity in the nucleus. The 
nuclear network surrounds this cavity, but is not in contact 
1 Loc. cit. 
