Hasseanthus Rose in N. L. Britton and J. N. Rose, New N. Amer. Crassul., 37. 1903

Stems underground, tuberous corms, mostly unbranched distally, ovoid to oblong, sometimes irregular. Leaves mostly withering by anthesis; petiole often strongly narrowed; blade terete or laminar, turgid except at very thin, broadened base. Cymes: branches commonly 2-3, simple; cincinni not or scarcely circinate. Pedicels absent or erect, to 3 mm. Flowers: petals ascending to spreading from near middle, corolla widely open; pistils erect to ascending or mostly widely spreading, separated in flower, somewhat gibbous in fruit.

Species 6 (5 in the flora): sw California, nw Mexico.

The underground corms of subg. Hasseanthus, and the leaves that wither in spring, seem clear adaptations to drought. Also, the plants are reduced in size and in lifespan. M. Dodero (1996) found that in the greenhouse the smaller ones could flower in five months from seed. From morphological and allozyme data, he concluded that the group is monophyletic, seeming close to Dudleya attenuata, the species of subg. Stylophyllum with the most-reduced leaves and inflorescence. He suggested that by paedomorphosis the underground caudex ("corm") probably evolved from the tuberous caudex he noted in Dudleya seedlings, which furthermore tend to be drought-deciduous, and that the leaves became smaller, with narrower and thinner petioles, as in the series from D. multicaulis through D. variegata and D. blochmaniae to D. brevifolia. Thus he found the adult leaves of D. brevifolia like the first seedling leaves of these other species.

Although in subg. Dudleya and Stylophyllum the leaves rarely become detached and take root, M. Dodero (1996) found that in subg. Hasseanthus they more often do. The leaves readily root at the base and quickly form new plants, most easily in those species with narrower leaf bases. Where wild plants were browsed by rabbits and rodents, he sometimes found detached leaves rooting. In the greenhouse, with species having smaller leaves, he even saw new rosettes formed in January and flowering by April.

SELECTED REFERENCES Clausen, R. T., R. V. Moran, and C. H. Uhl. 1945. The taxonomy and cytology of Hasseanthus. Desert Pl. Life 17: 69-83. Dodero, M. 1996. Phylogenetic Analysis of Dudleya Subgenus Hasseanthus (Crassulaceae), Using Morphological and Allozyme Data. M.S. thesis. San Diego State University. Moran, R. V. 1950. Notes on Hasseanthus, I. Desert Pl. Life 22: 76-82. Moran, R. V. 1951b. Notes on Hasseanthus, II. Desert Pl. Life 22: 99-105.