CHAPTER II 
THE SEXUALITY OF THE UREDINALES 
De Bary suggested in 1884 that, if there was any sexual act 
occurring in the life-cycle of the Uredinales, it would probably 
be found in connection with the ecidium. At that time 
nothing was known on this point, and De Bary anticipated that 
something might take place analogous to what happens in the 
formation of the asci of certain Ascomycetes. 
The first discovery was made by Blackman (1904), who 
found that, in laying the foundation of the spore-bed of the 
ecidium of Phragmidium violuceum, cells became binucleate 
by the passing into them of a 
nucleus from an adjoining vege- 
tative cell. He saw that this 
passage took place through a nar- 
row opening formed between the 
cells (Fig. 18). The binucleate 
cell then became the equivalent 
of an oospore, and formed the be- 
ginning of a sporophytic genera- 
tion. In other words, he supposed 
that the fertilised cell represented 
a female gamete and the vegeta- 
tive cell replaced a now vanished ae 
or functionless male gamete. The Development of ecidium (after 
fertilisation would then be of the Lapeer ERR Peed 
nature of a semi-apogamy. He cells below, a nucleus is seen 
considered that the spermatia ia iin Sides 
were the functionless male gametes. From the ‘cell to be 
fertilised he saw an upper sterile cell cut off, which soon 
G. U. : 2 
