Ontogeny of Teliospores of Cronartium Paraguayense and Relationship to Didymopsora

SUMMARY

The microcyclic Cronartium paraguayense Speg. was found not to belong in the genus Cronartium. It is redescribed and transferred to Didymopsora as D. paraguayensis (Speg.) J. L. Cunn. A KOH treatment of the herbarium material restored it well enough to enable study of the ontogeny of the teliospores, including nuclear relationships. The 2-celled teliospores are formed initially in chains arising from a mycelium-lined cavity in the host leaf. Binucleate basal cells divide conjugately to form alternately spore initials and intercalary cells. The spore initials divide making the young spore 2-celled. The two nuclei in each cell fuse, the spore wall thickens, and usually the component cells of the mature teliospore separate, although in mass they adhere to make a hard hair-like column. The ontogeny of the teliospores is basically similar to the ontogeny of catenulate aeciospores of other rusts.