Canadian Forest Service Publications
Studies of western tree rusts. II. Melampsora occidentalis and M. albertensis. 1955. Ziller, W.G. Canadian Journal of Botany 33(2): 177-188.
Available from: Pacific Forestry Centre
Catalog ID: 20772
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Observations at selected field locations and results of repeated inoculations have shown that Douglas fir is an aecial host of Melampsora occidentalis Jacks. A brief account of the rust's life history is given and the aecial state is described from a specimen obtained by inoculation. Arthur's diagnosis of the aeciai state of M. albertensis Arth. is replaced by a new description based on a specimen obtained by inoculation. Caeoma occidentale Arth. is shown to represent the pycnial and aecial states of Melampsora occidentalis, not M. albertensis. The aecial states of M. albertensis and M. occidentalis, both occurring on Douglas fir needles, are identical in gross morphology and time of appearance in nature, but can easily be distinguished from each other by spore size.