Chromosome Behavior in a Genus Cross.

Crosses between different genera of plants are rare and a satisfactory cytological study of such hybrids has never been made. A comparison of chromosome behavior in genus and species crosses is of interest in connection with a comparison of genetic and taxonomic relationships. A cytological analysis should also show the reason why crosses of genera are almost completely or quite sterile and whether there is any possibility of obtaining fertile progeny. Crosses were made between Aegilops cylindrica Host. and Triticum vulgare Vill. var. lutescens Korn., agronomic variety Marquis. Aegilops cylindrica is a wild grass distributed in Italy, the Balkans, South Russia and Asia Minor (PERCIVAL 1921). The culms are hollow and thinwalled and the outer glumes are rounded on the back. The rachis does not disarticulate into separate spikelets, as is the case in certain wild wheats, but is brittle as in T . Spelta. The terminal spikelets bear one or two long awns. Marquis IS one of the most important varieties of T . vulgare. It is an awnless spring wheat of high quality. The culms are 95 to 115 cm tall, which is about twice the height of the culms of Aegilops cylindrica. The heads of the two parents and the F1 hybrid are shown in plate 1. This photograph was obtained from Doctor E. F. GAINES, who happened to have the same hybrid in his experimental plots a t WASHINGTON STATE COLLEGE. These were planted in the greenhouse a t BUSSEY INSTITUTION in the fall of 1921. Two F, plants were obtained. These plants were unusually vigorous in vegetative development, but were completely sterile. The sterility of the F1 was also indicated by the appearance of the pollen grains which were obviously imperfect with very few exceptions. The F1 plants were more or less intermediate in appearance. Doctor GAINES has recently The cross of these two genera resulted in several seeds.