Generations , and General Cytology of the Uredineae . 361 
Endophyllum , in which binucleate aecidiospores, produced in a normal way, 
behave on germination like teleutospores, the two nuclei separating and 
uninucleate sporidia being produced (see Maire, 29), is just the opposite 
to the case discussed above. It is the transition from the asexual to the 
sexual generation without the intervention of the teleutospore (spore- 
mother-cell). It can therefore be compared with cases of apospory among 
the higher plants. Maire has described a case in Endophyllum in which 
the aecidiospore germinated in a normal way, but the life-history of the 
form is not known. 
There can be little doubt that the eu- and -opsis forms which possess 
the aecidium must be considered as more primitive and the other 
(apogamous) forms as reduced. The view of Dietel, that the lepto- and 
micro - forms which possess only teleutospores are the most primitive, and 
that the other forms are derived from them, can hardly be accepted in the 
light of our present knowledge. 
Heteroecism . As the heteroecious forms are confined to those 
possessing the aecidium, i.e. to the more primitive, it seems probable that 
heteroecism may not be, as generally conceived (see Klebahn, 27), a later 
adaptation, but may actually be the primitive condition in the group. 
Although we are ignorant of the origin of the group it is possible to 
conceive that the sporophyte was first developed in connexion with life 
on another host, just as the sporophyte in the higher plants seems to have 
been developed in connexion with a new terrestrial existence. The 
autoecious eu- forms would then be the first step in reduction — a purely 
environmental one ; later a morphological reduction of the number of spore- 
forms would appear to have taken place. 
Fusion in the Basidium. 
The fusion of nuclei in the basidium of the Basidiomycetes is exactly 
comparable to that in the teleutospore, for it has been shown by Maire (30) 
in the case of a large number of forms, and also by Harper (21) in two 
cases, that in this group, also, the two nuclei which fuse are conjugate nuclei, 
the ancestors of which have been associated together for a number of 
generations. It is clear then that the view of Dangeard and others, which 
considers this fusion as a process of fertilization, is quite untenable. The 
stage at which the nuclei first become conjugate is unknown, but it is there 
that one must look for a process of fertilization, and not to the fusion in the 
basidium, which, like that in the teleutospore, is a process of mere nuclear 
reduction, and (like chromosome-reduction) the necessary sequence of 
fertilization if the sexual cycle is to be completed. 
As the Basidiomycetes are apparently without anything which could 
be considered even as a reduced form of sexual organ, it is suggested that 
the conjugate nuclear condition, the transition from gametophyte to 
