|Abstract or Summary
- A biosystematic study was made on the species of Hackelia of
northwest America and adjacent Canada. During the course of the
study 140 populations, representing all species and varieties, were
transplanted to the greenhouse for study under controlled conditions.
Chromosome counts were made for all 14 taxa studied, and intra- and
interspecific hybridizations were attempted. For the study over
3000 specimens were borrowed from 21 herbaria in the United States
Only two chromosome levels were found: 2n=24 and 2n=48.
Chromosome counts were obtained only from mitotic cell divisions,
as some difficulty was encountered in making usable pollen-mother
cell smears. This was especially true in the tetraploids, where
normal chemical techniques for fixation of buds resulted in the
chromosomes tending to stick together. Because none of the species
have chromosome numbers higher than tetraploid, it was felt that
polyploidy, although present, has not been a dominant evolutionary
mechanism in this section of the genus. The tetraploid taxa under
study probably evolved from one or two original tetraploid ancestors
which underwent speciation during the Quaternary period.
It was found that nutlet features were of limited value as
taxonomic characters in some species of Hackelia. The nutlets of
some species are highly variable with regard to surface texture,
number and size of intramarginal prickles, and the length and degree
of fusion of the marginal prickles, The features of the fornix
of the corolla are also variable and must be used with care.
The distinctness of the tetraploid taxa is maintained in part
by their specific habitat requirements. They occur principally
in open sites with rocky to sandy soil, where plant competition is
An artificial key to the species and varieties is presented in
the taxonomy section, together with complete synonymies, descriptions,
lists of cited specimens, and maps of distribution.
One new species is described from southeastern Oregon (Hackelia
ophiobia) and one new variety from central Washington (H. hispida
var. disjuncta), Hackelia diffusa (Lehm.) Johnst. is defined to
include var. diffusa, var.arida (=H. arida (Piper) Johnst.) and var.
cottonii (=H. cottonii (Piper) Brand).