A Group of Tetraploid Roses in Central Oregon

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Abstract
Cytological material from Rosa durandii, R. myriadenia, and R. yainacensis showed that these are balanced tetraploids with 14 pairs at diakinesis. A semisterile R. nutkana was hexaploid. These tetraploid roses resemble R. nutkana in the size of flowers and hips, and in inflorescence type. In the number of stamens, fine serrations of the leaflets, size of pollen grains, and amount of sterile pollen they resemble the tetraploid R. californica. This tetraploid group seems to have a limited range, perhaps from central Oregon to the northern counties of California. It may have originated from a crossing between R. nutkana and R. californica. Some other rose species of limited range in this area may belong to this group. They are R. delitescens, R. brownii, R. calavera, R. pinetorum, and the forms in northern California usually classified as R. muriculata. Pollen grain size might be used in distinguishing the tetraploid and hexaploid rose forms in herbaria. The cubes of the mean length of the pollen of diploid, tetraploid, and hexaploid are as 11.7:1.9.