FUNGI, THE RUST FUNGI 



3 11 



nucleus from one cell into another one above, or laterally situated, in other 

 cases (fig. 264). The cluster-cup spores develop in chains from this basal 

 cell (or fertile cell) each having two nuclei. 



Fig. 263. 



Section through leaf of barberry at point affected with the cluster-cup stage of the wheat 

 rust; spermogonia above, aecidia below. (After Marshall-Ward.) 



When these binucleated cluster cup spores germinate and form the myce- 

 lium of the red rust stage (paragraph 463), each cell of this mycelium has two 

 nuclei. The red rust spores also have two nuclei, as well as each cell of the 



Fig. 264. 



Fertilization and development of aecidiospores in a rust, Phragmidium violaceum. ef>, epi- 

 dermis of host. 5/, sterile cells at ends of a-cidial thread, fc, fertile cells. A , part of accidial 

 stroma, showing two binucleate, fertile cells. B, showing nucleus of sperm cell at base of 

 fertile cell passing into the fertile cell at the side. C, similar stage. D-G, different stages in 

 formation of rccidiospores. H, mature rccidiospore. (After Blackman.) 



mycelium which they produce. In like manner each cell of the black rust 

 mycelium is binucleate up to the cells of the young teleutospore (paragraph 

 465). As the teleutospore matures the two nuclei unite into one. From this 



