THE FLORAL MORPHOLOGY OF THE POLEMONIACEAE

Abstract

THE POLEMONIACEAE, comprising twelve genera and about three hundred species, while clearly defined as a natural order of plants, show unusual difficulties in the determination of generic relationships. The entire group is so closely interrelated that absolute characters, which could serve as a basis to separate genera and species taxonomically, are lacking. Since the time of Jussieux (1789) this family has presented an interesting but baffling problem for systematists. Authors have differed widely in their definition of genera. This uncertainty of status is reflected in the confusion of nomenclature existing today, as well as in the wide variations of opinions regarding the merging or segregation of genera and species. Not only have problems arisen within the family, but differences of opinion on derivation and origin are met with on every hand. The uncertainty extends from the suggestion of Rendle (1925) that the Polemoniaceae came from a sympetalous type akin to the Rosales, to that of Hutchinson (1926), who assigns their derivation to the Geraniales. Moreover, Hallier (1905) and Bessey (1915) have considered the family to be an advanced type derived from the Primulaceae. Recent investigations in floral anatomy have demonstrated the fallibility of interpreting floral structures on general morphological features alone. In view of this fact, a careful study of the vascular structure of the flowers and fruits of the Polemoniaceae, together with representative forms of the Caryophyllaceae and Geraniaceae, was made to determine, if possible, the relationships existing both within and without the group. The writer wishes to express her gratitude to Dr. Arthur J. Eames of Cornell University for his assistance and kindly criticisms in this study. Her grateful thanks go to several contributors of material, among them Dr. David Keck of the Carnegie Institution at Washington, Dr. John Thomas Howell of the California Academy of Sciences, Dr. P. A. Munz of Pomona College, Dr. Fred Emerson of the New Mexico Normal University at Las Vegas, New Mexico, Mr. George Peranian of Utah Agricultural College at Logan, Utah, Dr. A. J. Sharp of the University of Tennessee at Knoxville, Tepnnessee, and to Dr. Minna Koch for her many helpful suggestions. The taxonomic treatment used as a basis was that of A. Brand in Engler's Das Pflanzenreich (1907). Representatives from each of the twelve genera, including about 125 species, were examined. For this purpose flowers and fruits in various stages of development were prepared by fixing in 70 per cent alcohol and embedding in paraffin. Complete serial sections were then cut 12 ,. in thickness and stained with crystal violet and erythrosin (1926). FLORAL STRUCTURE.-The Polemoniaceae, a family comprised of annual, biennial, and perennial herbs,