To clarify the limits betweenH.depressum(Scribner amp; Smith) Rydberg and its close and remote allies,H.intercedensandH.pusillum, respectively, we carried out morphological and cytological examinations and various statistical analyses including classifactory discriminant analysis, canonical discriminant analysis, and logistic discrimination. We concluded thatH.depressum, a tetraploid species, can usually be morphologically separated fromH.intercedens, a diploid species with which it is most frequently confused, by the maximum width of the lateral lower glumes. Those ofH.depressumare 0.1ndash;0.5ensp;mm wide, whereas those ofH.intercedensare 0.4ndash;1.3ensp;mm wide. Very few specimens will fall in the area of overlap between the two species. In these cases morphological identification can be ascertained by the lodicules, which inH.depressumhave an obvious and glabrous side lobe, whereas if there is a lobe inH.intercedens, it is rather small and beset with hairs at the margins. Populations ofH.depressumare often large and occur in the intermontane region of northern and central California, whereas those ofH.intercedensare typically small and occur along the coast of south California and Baja California. These two species are sympatric to a small degree, whereasH.pusillumdoes not occur in south and Baja California but is found throughout the United States and a few adjacent places in Canada. Other morphological and statistical findings are discussed.
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