Nature, 117(2945): 517 (1926)
The Evolution of Rosa
T. D. A. COCKERELL
University of Colorado, March 4.

FIG. 1.—Fossil Rosa Wilmattae Cockerel, from the Miocene of Florissant, Colorado.

THE recently published paper of Dr. C. C. Hurst ("Experiments in Genetics," 38, 1925) on the chromosomes and characters in Rosa may well mark a new epoch in biology. We must await the appearance of his monograph for full details, but as he suggests, we may in the meanwhile try to apply the Rosa principles to other plants and animals. It is suggested that the common ancestor of all roses was a northern decaploid species, at present unknown.* The various forms could have arisen by the dropping out of sets of chromosomes, the existing five diploid types being the end-products of this process. We are told, however, that "certain cultivated triploid and tetraploid forms are obviously duplicated forms which have arisen … by duplication of the septets of chromosomes." These maintain the essential specific characters of the original diploid species, instead of showing a complex of the characters of diverse septets. Is it not possible to suppose that this duplication may have been the first step in the production of polyploid species, the latter acquiring the diverse septet characters by successive mutations

The Drosophila work has shown that mutations are likely to be lethal or unfavourable. In a diploid species such mutations should apparently work more havoc than in a polyploid one. Polyploidy might then be a condition favouring the survival and accumulation of mutated genes, resulting after very long periods of time in diversity of the septets. Such diversity might come to have its advantages, as Dr. Hurst indicates, in specific cases. On the other hand, in some cases the shedding of a septet might be advantageous, getting rid of some undesirable features, and producing a more uniform or consistent type. Thus the diploid R. rugosa, which I found to be a strictly sea-coast plant in Siberia, is a well-defined type specially adapted to its peculiar habitats but not extending even a few miles inland. Yet it is not to be expected that the diploids will all be successful, and close field study combined with cytological research may be expected to reveal a variety of forms with reduced chromosome numbers, coming into existence only to perish at once or in a few years. Many, probably, may not even be capable of development.

Possibly, then, there is a double process going on, and it may not appear certain that the original rose was decaploid, though the existing diploids may all be derived from polyploid ancestors. There has been time for much to happen, for we know from the Miocene of Florissant several species of roses extraordinarily like those of the present day (cf. Fig. 1).

*CybeRose note: In the same work, Hurst wrote, "The fact that the polyploid species show the combined characters of the five diploid species seems to support the idea of origin by hybridisation and duplication."


The Scientific Monthly, 19: 415-433 (Oct 1924)
A JOURNEY IN SIBERIA
Professor T. D. A. Cockerell
University of Colorado

p. 420
Our first excursion, under the direction of our guide and interpreter, Mr. Lavrushin, was to Okeanskaja, a sort of suburb about an hour's train journey distant, on the Gulf of Amur. It is not on the open ocean, as the name might suggest, but on a secluded and shallow bay, where the water is calm and warm, and the people come in great numbers during the summer to bathe. There is no town, properly speaking, but only a great number of small houses or cottages among the trees, often with very beautiful gardens. These summer cottages, known as datchas, are delightful places to spend the hot summer months, and the fare on the train, for those who have to work daily in the city, is very small. We were surprised, however, to hear a friend state that she and her little daughter wished to go to their datcha, but did not know whether they could, as it was necessary to get a medical certificate. I supposed of course that the certificate would show the absence of infectious diseases, but this was an entire misconception. The Communists had looked with displeasure on these evidences of bourgeois luxury, but concluded that it was quite legitimate for people to live at the seaside if they were out of health and needed recuperation. So far as we could judge, there was little difficulty in getting the required certificates, and the cure generally seemed to be extraordinarily rapid. But I am not the one to scoff, for it actually happened, later on, that a beatific day at Mme. Polevoi's was the turning point in a bad attack of bronchitis which I had developed in the hills.

Almost the first thing we noticed, on getting off the train at Okeanskaja, was an abundance of the familiar Rosa rugosa of our gardens. Here it is a wild plant, and it was very interesting to see that it was confined to the immediate coast, its thick leaves being an adaptation to maritime conditions, though retained when it is artificially grown inland. Maack, who explored the Ussuri country long ago, and collected the flora extensively, evidently did not visit the coast, for he did not get Rosa rugosa at all, but only species then referred to as R. cinnamomea and R. acicularis, very similar to our wild roses of the Rocky Mountains. I looked for parasitic fungi on the R. rugosa at Okeanskaja, but found only a very sparing infestation, which Dr. Arthur tells me is Phragmidium rosae-rugosae Kasai, so far as it is possible to determine from the aecial stage alone.