366 Blackman . — On Ike Fertilization , Alternation of 
respectively from the two nuclei of the teleutospore, but are not always 
present. In the first division of the promycelium of G. clavariaeforme 
they can be seen to be formed by the aggregation of a number of chromo- 
somes ; in the other divisions they are formed directly, by the condensation 
of the chromatin of the nucleus. 
In those Uredineae which have a reduced life-cycle without an aecidium 
(, brachy hemi -, micro-, and lepto- forms) the transition from single to paired 
nuclei, and from gametophyte to sporophyte, apparently takes place in 
connexion with the uredospores, or if these are absent, in connexion with 
the teleutospores. Such a shortening of the life-cycle is comparable with 
the case of cipogamy among the higher plants ; the cytological details are 
not yet known, but it is possible that it is brought about by the association 
of the nuclei of two vegetative cells (cf. apogamy in ferns). 
The peculiar shortening of the life-cycle to be observed in Endophyllum , 
where the binucleate aecidiospore germinates like a teleutospore and the 
uninucleate condition is brought about by the simple separation of the two 
nuclei, is clearly a transition from the sporophyte to the gametophyte 
without the intervention of the teleutospore (spore-mother-cell), and should 
accordingly be considered as comparable to apospory in the higher plants. 
The fusion of paired nuclei in the basidium of the Basidiomycetes is 
exactly comparable with that in the teleutospore, and should also be con- 
sidered, not as a process of fertilization, but as a purely secondary process 
of nuclear reduction preliminary to chromosome reduction. 
How the condition of paired nuclei is brought about in the Basidio- 
mycetes is not yet clear. The life-history of these forms seems comparable 
with that of the lepto- forms among the Uredineae, and it is suggested that, 
in the absence of sexual organs, the transition from single to paired nuclei, 
i.e. the transition from gametophyte to sporophyte, is brought about 
apogamously in a similar way. 
The Uredineae and Basidiomycetes show an obvious relationship, 
for both have paired nuclei at some stage of their life-history, and in both 
groups the individuals of certain pairs fuse together in specialized reproduc- 
tive cells, a fusion to be followed by synapsis and a tetrad division. The 
Uredineae with their sexual organs would certainly seem to be more primitive 
and can hardly be classed as a mere subdivision of the Basidiomycetes. 
The Uredineae appear to show a relationship with the Florideae among 
the Algae. 
The aecidium of Phragmidium with superficial position and very simple 
structure without a pseudoperidium is really not a definite organ, but a mere 
ill-defined sorus of reduced, female reproductive organs ; it is no doubt 
primitive , while the typical aecidium with its pseudoperidium and deeper 
point of origin is a definite organ, and is probably a later development. 
The binucleate condition of the sporidium exhibited by Phrag . 
