Showing papers by "G. Ledyard Stebbins published in 1949"
Journal Article•
TL;DR: In the large genus Solanum, perhaps the most widespread species-group is that contained in the section Morella^ and centering about SolAnum nigrum L., often known as "deadly nightshade," which consists of weedy perennials or annuals, many of which have become adventive in regions far from their original habitats.
Abstract: In the large genus Solanum, perhaps the most widespread species-group is that contained in the section Morella^ and centering about Solanum nigrum L., often known as "deadly nightshade." It consists of weedy perennials or annuals, many of which have become adventive in regions far from their original habitats. In addition, practically every continent and floral region has its indigenous members of the complex. These facts, as well as the great variability of the species, combine to make the group very difficult taxonomically. Many of the more conservative botanists, such as Gray (1886, p. 227) recognize only one species in the entire complex. On the other hand Dunal (1852, pp. 28-387), in his monographic treatment of the genus has recognized no less less than 53 species in this section. An even larger number has been recognized by Bitter (1912, 1913) in his several publications on the genus. Various members of the complex have from time to time been subjected to cytogenetic analysis. Jorgenson (1928) dealt primarily with the European species, true S. nigrum L. and "S. luteum" (= S. mllosum Lam.). He showed that these two species have different chromosome numbers, 2n = 72 and 2n = 48 respectively, and can be hybridized only with the greatest of difficulty. Nakamura (1937) found that the plants growing in Japan and classified as S. nigrum actually comprise two distinct species, the typical S . nigrum with 72 chromosomes and a diploid with 24 chromosomes, which he named S. photeinocarpum Nakamura. Cytological studies by other authors (Tokunaga 1934, Ellison 1936) have confirmed the existence of several different chromosome numbers within the complex. Our attention was called to this complex by two observations. In the first place, the senior author noticed that the small-flowered straggling perennial which passes as S. nigrum in California looked obviously different from the larger flowered, thin-leaved annual which he had previously recognized by that name in the eastern United States. A count of its chromosomes showed that it was a diploid, with 2n = 24 chromosomes. In the second place, the junior author continued an exploration of the complex, only to find that two different chromosome numbers exist among the plants passing as S. Douglasii Dunal. Plants from the San Francisco peninsula were hexaploids with 2n = 72 chromosomes, while those from Monterey, the type locality for the species, and
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