1917, John William Harshberger, A Text-Book of Mycology and Plant Pathology (P. Blakiston’s Son & Co.), chapter XIX, page 199:The European C. asclepiadeum has its æcia on the branches of Pinus silvestris in May and June, and its urediniospores and teliospores on Pæonia officinalis in gardens, as also on Vincetoxicum, Cynanchum and Verbena. C. quercuum has its æcia on Pinus and its urediniospores and teliospores on at least twenty species of oak in North America.
