Generations , and General Cytology of the Uredineae . 357 
conceivable that in such a highly developed group as the Uredineae we 
should witness the evolution of mitotic division. The second division with 
its very complex achromatic mechanism but simple method of chromatin 
segregation points clearly to the process being a reduced one. 
A comparative study of nuclear division in the Uredineae with that to 
be observed in the Basidiomycetes would be of great interest, and, con- 
sidering the obvious relationship of the two groups, might throw some light 
on the question as to whether the reduction in nuclear mechanism in the 
former group is to be connected with the marked parasitic habit. The two 
chromosomes described by Maire (30) as universal for the Basidiomycetes 
are doubtless merely chromatin masses, comparable to those described 
above. Wager (55, 56), Ruhland (47), and Harper (21) have all shown 
that in the forms they investigated the chromosomes in the basidium were 
much more numerous. Maire seems to have observed such structures in 
certain cases, but he applies to them the term ‘ protochromosomes,’ and states 
that they fuse later to form the two structures which he believes to be 
the real chromosomes. This is exactly what happens in some cases in the 
promycelium in G. clavariaeforme (Fig. 30 ), but there can be no doubt, as 
the figures show, that the first-formed structures are the true chromosomes. 
With reference to the question of the function of the nucleus and the 
relation of direct to indirect division, the existence of a group of Fungi, 
which in the whole life-cycle show but one, or perhaps two, divisions in 
which there is a distinct formation of chromosomes, is certainly a very 
interesting fact. The view that direct nuclear division is confined to cells 
which are in a senile state has of late years been largely modified. It has 
been shown that a number of Protozoa and certain animal cells divide 
normally in an amitotic manner, and Nathansohn (39) has shown for 
Spirogyra , and Shibata (50) for Podocarpus , that cells which have divided 
amitotically can later divide in the ordinary mitotic manner. Similarly 
Hacker (19), Wasielewski (58), and Nemec (40) have shown that nuclei 
which have divided in an abnormal 1 way under the influence of narcotics 
can again divide in the normal indirect manner when placed under natural 
conditions. 
These observations are generally considered to show that the nucleus 
has remained entirely unaffected by the intercalation of one or more direct 
divisions in the normal series of mitoses, but they really prove no more than 
that the effect (if any) has not been sufficiently profound to destroy their 
power of normal division or to prevent them carrying on their normal 
development within the limits of the experiment. Nemec has pointed out 
1 There seems considerable doubt as to how far these divisions are abnormal. Wasielewski 
considers them to be of the nature of amitoses, while Nemec brings forward very considerable 
evidence to show that they are merely modified indirect divisions in which, however, there is still 
an exact halving of the chromatin. 
C C 7 , 
