46 Blackman and Fraser . — Further Studies on the 
sporophytic stage with conjugate nuclei before the occurrence of spore 
formation. 
The sporophyte stage, with its three kinds of spores, is always very 
well marked in the forms with the full life-cycle, but in forms like Puccinia 
Malvacearum it is represented only by a few generations of cells with 
conjugate nuclei. 
The actual chromosome-reduction no doubt takes place during the 
first division in the promycelium, but as the fusion of nuclei in the 
teleutospore is clearly the preliminary to reduction it is convenient to 
make that fusion the starting-point of the gametophyte. 
In the -opsis forms, which are not indicated in the diagram above, the 
mycelium arising from the aecidiospores gives origin directly to teleuto- 
spores. 
The Basidiomycetes have clearly the same general and cytological 
life-history as the lepto - and micro - forms among the Uredineae, as pointed 
out earlier (1). In this group neither the method nor the exact point 
