(Feb 1917)  Page(s) 113-4.  
 
"Imperfection of Pollen and Mutability in the Genus Rosa" by Ruth D. Cole
During the winter of 1915-1916 I made a study of all the species, of which specimens were obtainable, of the genus Rosa.  This was done in connection with work on other genera of the family Rosaceae, notably on Rubus and on Crataegus; and it has been interesting to note that in all 3 genera there is indication of a large amount of hybridism, and that the multiplication of species is startlingly great. [...]
For nearly a century it has been known that one of the most important and most easily recognized characteristics of a hybrid is imperfect pollen. [...] Since, therefore, imperfect pollen is a well known characteristic of hybrids, and one of the easiest means of identifying them, it is from an examination of the pollen of the species of Rosa that their probable genetic status can be determined most easily.
...normal pollen is perfect morphologically, fully formed, and having normal protoplasmic contents; while abnormal or imperfect pollen, such as often characterizes known hybrids, on the contrary, is usually shrivelled and has little or no protoplasmic contents, consequently making the grain quite impotent.
The pollen of Rosa is largely in the last named condition, imperfect, and therefore probably sterile to a considerable extent.  Of the 32 species secured from the Arnold Arboretum, 2 show entirely perfect pollen, and in 3 others imperfectly developed grains were slightly intermingled; that is, showing only 1-10 per cent bad pollen.  Seventeen show a very large percentage of imperfect grains (about 50-100); and the remaining 20 show 10-50 per cent.
In the ... much larger group the percentage of imperfect pollen is 10-50.  In this group are R. spinosissima altaica, R. spinosissima (garden variety hybrid), R. spinosissima, and R. spinosissima paniculata (garden variety).  R. spinosissima fulgens (garden variety), because of its larger percentage of undeveloped grains, belongs to the third and last group [having 50-100 per cent imperfect pollen].
...In comparing the species R. spinosissima with the recognized garden hybrid, a variety of the species and called R. spinosissima garden variety hybrid (fig. 10), the latter shows less pollen in the loculus, but about the same percentage of shrivelled grains.  R. spinosissima paniculata, another garden variety, has only about 10 per cent of its pollen grains undeveloped; while still a third garden variety, R. spinosissima fulgens, has a larger percentage than any of the group I have examined.  This last, as may be seen in fig. 11, has an abundance of pollen grains in the loculus, but about 50 per cent of them appear as tiny, shrivelled cells.
 

(1888)  Page(s) 301.  
 
There is an abundance of wild roses of different hues, all of which belong to the same species, Rosa Arkansana.

(May 1929)  Page(s) 455, vol 87, no 4.  
 
Cytological Conditions and Evidences for Hybridity in North American Wild Roses
Eileen Whitehead Erlanson
These bristly varieties of R. blanda when collected in the western parts of its range are usually named R. macounii. R. macounii is probably a composite species, consisting in part of pubescent varieties of R. woodsii (most botanists so interpret R. macounii), and in part of more robust forms which should be placed in R. blanda var. hispida.

(Dec 1934)  Page(s) 207, vol. 96, no. 2.  
 
EXPERIMENTAL DATA FOR A REVISION OF THE NORTH AMERICAN WILD ROSES
EILEEN WHITENEAD ERLANSON
p. 207
3. HARDINESS AND CLIMATIC TOLERANCE.—Cultures at the Botanical Gardens of the University of Michigan showed that some of the roses of the Pacific Coast region were only partially hardy in southern Michigan. R. californica, R. pisocarpa, and R. gymnocarpa grew very slowly, seldom flowered, and were often cut back by frost or winter killed. R. woodsii was very variable in this respect. Plants or seedlings from British Columbia, Washington, the Rocky Mountains, and the Great Plains thrive in Michigan. Plants or seedlings from the arid Great Basin persisted in Michigan but were stunted; they lost their leaves during the summer drought and never flowered. These two physiologically different groups within R. woodsii show a parallel series of variations, and cannot be distinguished morphologically.