The genome may be viewed as a harmoniously coadapted and integrated gene ensemble which mediates a broad and complex array of developmental processes whose successful completion is essential for viability, vigor, and fertility. The genomes of related species, while possessing these attributes, differ in their genetic constitution and in the type of epistatic interactions which confer maximal fitness. Consequently, these genomes may not be capable of interacting in a harmonious fashion, when joined in an interspecific hybrid. Genome incompatibility in hybrids may be based upon negative interactions between parental genes and chromosomes, embryo and surrounding tissues, genes and cytoplasm, and plastids and cytoplasm, and will be expressed in the form of hybrid inviability, weakness, and sterility (cf. Stebbins, 1958; Grant, 1963). The antagonisms which are manifested prior to germination or during reproduction have been critically analyzed in numerous plant genera. On the other hand, relatively little is known of the antagonisms which underlie the development of the plant body. The development of any expression is to some extent resistant to modification by fluctuations in the external or internal environment (Waddington, 1961). This resistance or buffering is conferred by regulatory interactions during morphogenesis which are mediated by complex feed-back mechanisms. When these interactions are interrupted or disrupted by stress generated by the external environment or the genotype, development deviates from the prescribed geometry, and intragenotypic variability in repeating or paired structures ensues. Interspecific hybrids by virtue of the lack of coadaptation of their genomes may be expected to experience developmental instability to a greater extent than their parents when exposed to the same environmental regimes. Such has been observed in hybrids of Antirrhinum (Lotsy, 1916; Stubbe, 1959, 1963), Aesculus (Hardin, 1957), Geum (Gajewski, 1953), Digitalis (Schwanitz, 1957), Lycopersicon (Rick and Smith, 1953; Tal, 1967), Gilia (Grant, 1956), Layia x Madia (Clausen, 1958), Phyllanthus (Webster, 1959), Baptisia (Alston, 1965), Linanthus (Huether, 1966), Phlox (Levin and Levy, 1970) and many genera of ferns (Wagner, 1962). The present study was undertaken with the hope of demonstrating the effect of hybridity on developmental stability. Three species of Liatris (L. aspera Michx., L. cylindracea Michx., and L. spicata Willd.) and their natural hybrids were chosen as experimental material because hybrids were abundant, and the species are distantly related (Gaiser, 1946). Furthermore, there is a good deal of information on the genetic and ecologic structure of the population which the hybrids and species comprised (Hadley and Levin, 1967; Levin, 1968, 1969). For a comparison of the salient morphological attributes of the species and hybrids the reader is referred to the aforementioned papers. Suffice it to say that the hybrids are quite distinctive and vigorous.