The effect of isolation is particularly impressing, when the combined differences (D²-values) of the 3 quantitative characteristics (length and number of stems and number of the flowers) are taken into consideration. The D²-values among the populations increase with their geographical distance.

There are also striking differences in the degree of selffertility among 16 "minor" populations. The selffertility varies from 1.51 to 56.4% that is very high when compared with the cultivated rye-variety "Petkuser" which amounted to 3.5% only. A distinct correlation was found between the degree of selffertility and the amount of segregating lethal or sub-lethal types in the following inbreeding generation: the higher the selffertility, the lower the lethality in the progenies.-Two collection samples of the species Secale Vavilovii with a fragile rachis proved to be completely selffertile: the seed setting showed approximately after selfing the same percentage as that in the open pollinated plants, i.e. 49.2% in 1955 and 45.4% in 1956 respectively. The progenies after selfing neither segregated into lethals and sublethals nor exhibited any depressions of inbreeding. The flowers are kleistogame and that is certainly the reason why hybridization does not occur with plants of other rye types in the immediate neighbourhood. Kleistogamy is to be considered as a species barrier preventing hybridization.

With regard to the evolutionary problem our studies on Iranian rye populations confirmed the hypothesis of a polyphyletic origin of the cultivated rye as inaugurated by Roshewitz.

The determination of 343 original ears by means of the key for classification of varieties as used by Vavilov and his scholars, did not bring about any kind of results in the analysis of varieties. The varieties established by this method have no clearly defined areas of spreading but are mixed invariability and at random in the northern and western districts of Iran so that genetical relations among the population can not be detected in this manner.

The ideas of Stebbins, however, which consider the natural populations to be the genetically efficient entities in the process of evolution which inspired also the present investigation seemed us to be in many respects very fruitful for an analysis of an extensive collection.

(Received Oct. 15, 1957)