Chromosome Numbers in Hemerocallis, with Reference to Triploidy and Secondary Polyploidy by A. B. STOUT the New York Botanical G

250 Cytologia 3 Chromosome Numbers in Hemerocallis, with Reference to Triploidy and Secondary Polyploidy By A. B. STOUT The New York Botanical Garden ReceivedFehruaiy 22, 1932 The condition of triploidy in certain members of the fulvous daylilies has been reported by Belling (1925) and by Takenaka (1929). Evidently Belling studied the Linnaean type of the species Hemerocallis fulva that has long been propagated asexually as a garden clon in Europe and America and for which the writer (1929 a) has suggested the horticul tural name "Europa Daylily" Takenaka reported triploidy in what he calls the H. fulva of Linnaeus, in a double-flowered clon which he calls H. disticha var. Kwanso, and in another but unnamed type. Both Belling and Takenaka agree that the triploid number in the plants they studied is 33 and their assumption is that there are three sets of 11 each. Takenaka also reports a diploid number of 22 for plants of H. flava, which is in agreement with the number reported by Nawaschin (see Tischler, 1927), and for plants considered as H. aurantiaca Baker, H. Middendorffii Traut. and Mey., H. disticha Donn, H. longituba Miq., and H. minor Miller. A rather extensive survey of the chromosome numbers has now been made by the writer" for the species, several clonal varieties, and various seedlings of Hemerocallis assembled at The New York Botanical Garden which shows (1) that a somatic number of 22 chromosomes is the rule for all species of the genus, (2) that triploidy exists in several of the cultivated clons of fulvous daylilies, and (3) that diploids, triploids, aneuploids and para-triploids are to be obtained among the seedlings of diploids crossed with triploids. * The author is indebted to assistants for the preparation and preliminary study of the cytologicalmaterial and especially to Miss Clyde Chandler, technical assistant to the writer. 1932 Chromosomenumbers in Hemerocallis,with reference to triploidy 251 The Purely Diploid Species Twenty-two chromosomes have been found to be the rule in the early equatorial plates during the mitoses of root-tip cells for all individuals thus far studied of the following species: Hemerocallis flava, H. minor, H. Dumortierii, H. Middendoriffii, H. aurantiaca, H. Thunbergii, H. citrina, H. Forrestii, H. multiflora, H. nana and H. plicata. In various cases deviations in the number were observed giving counts of 21, 22, 23 and 24 for the same plant. Descriptions with colored plates of all the types of these species which were studied, except for the two named last, have been published (Stout, 1929c, 1930). The Species Hemerocallis fulva It is now certain that the cultivated horticultural plant described by Linnaeus as Hemerocallis fulva is merely a triploid clon which is so completely self-incompatible that it never produces seeds to self-, close-, or intra-clonal-pollinations. That the original plant of this clon was derived from some diploid species is obvious. A survey of the fulvous daylilies closely related to this Europa Daylily has already been presented by the writer (1929a and b) and this indicates that a somewhat variable wild type of fulvous daylily is widely distributed in China and Japan which maybe considered as the species H. fulva. This group would include the H. disticha of Donn, and the H. longituba of Miquel. Living plants, showing a considerable range of minor variations, but all here considered as included in the species H. fulva, have been obtained from various localities in China and Japan. In several cases these plants came from what was certainly wild stock reproducing by seeds. No two plants were exactly alike and seeds were readily obtained by intercrossing. In these plants the normal number of diploid or somatic chromosomes is 22. The Europa Daylily. It seems very probable that all of the various cytological studies, at least by investigators in Europe and America, previously reported for "H. fulva" have been made on plants of the one clon, the Europa Daylily. The estimates of the haploid chromosome number, based on the grouping of chromatin units in the reduction divisions, have been 12 (by Strasburger, 1882; Timm, 1928), 16 (Tischler, 1927), and 24 (Schtirhoff, 1926, p. 461). Belling (1925) was the first to interpret the grouping of chromosomes in this plant during meiosis as fluctuating about the number eleven. In the prophases of the second 252 A. B. STOUT Cytologia3 division he made some counts of 33 split or X-shaped chromosomes and concluded that the plant is a triploid, but he notes that it is an irregular triploid with varying numbers of trivalents, bivalents, and univalents in meiosis. A somewhat extensive study of the many irregularities in chromo some behavior in the stages of sporogenesis and in somatic divisions for plants of the Europa Daylily was reported by Stout and Susa (1929) in which it was considered that the variations arise from a basic somatic number of 12 as a result of fragmentation, non-distribution, and non disjunction. A total of only six chromatin masses were sometimes found in the equatorial plate of the first division in meiosis, groups of six apparently single chromosomes were frequently seen in the late stages of the second division, and in these stages a total of 24 was frequently found. Also in the division of the primary nucleus of the pollen grains a minimum number of 6 was found. Variations were also found in the number of chromosomes in somatic cells where the number frequently rises well above 33, and especially in the older tissues of the root-tip there is evidence of variation to lower numbers due to non distribution. But a further study of the same plants now shows that 33 chromosomes are usually to be found in the early stages of the equatorial plate in somatic divisions especially in the undifferentiated tissue or close to it. Since the somatic number for the other species and for the wild plants of the fulvous type is 22, the haploid number characteristic of the genus H. fulva is to be considered as 11 and the clon Europa is to be regarded as a triploid. A group of triploid plants all identical in character and evidently of a single clon was obtained from Takyu, Korea, through the kindness of Mr. T. Susa. The flowers of these plants appear to be the same, or nearly the same, as those of the Europa Daylily but further comparison awaits the time when these plants become well established and of mature stature. The clon Europa was in cultivation in Europe as early as 1576 (Lobel, 1576) but it is possible that it also exists widely as a cultivated plant and as an escape in the Orient. The clon Maculata. This clon was derived either from seed or from a living plant sent from Shen-si, China to Florence, Italy about 1897. Although originally described as a true botanical variety, the plant has only been propagated vegetatively as a garden clon. The Maculata Daylily (for colored plate and more complete description see Stout, 1929 c) closely resembles the Europa Daylily but the flowers are larger, 1932 Chromosomenumbers in Hemerocallis,with reference to triploidy 253 slightly different in coloring, and the flowering begins somewhat later in the summer. There is much abortion of pollen, and there is complete self-incompatibility, but fruits and a limited number of viable seeds per capsule are readily obtained from certain compatible cross-pollinations. The chromosome counts in the root-tips of plants of this clon are most frequently 33 and the clon is evidently a triploid. The double-floweredfulvous daylilies. The varietal names "Kwan so" and "flore-pleno" have been given to certain double-flowered daylilies that are very similar to the Europa Daylily in habits of growth and flower colors. These are propagated exclusively by division and have evidently long existed in China and Japan where they appear to have escaped widely from cultivation. Plants of the double-flowered type were not brought to Europe and America until about 1860 (see Stout, 1929 a). Plants have been received at The New York Botanical Garden under the names "Kwanso" and " Flore Pleno" from various nurserymen and from various botanical gardens. The counts of chro mosome numbers in root-tips of these have, as a rule, been 33, as reported for the plants of "Kwanso" studied by Takenaka. A study of the cytology of sporogenesis in "Hemerocallis fulva fl. ploeno" by Sienicka (1929)reports "16 gemini" in stages of diakinesis and many irregularities in the later stages of meiosis and spore formation. It seems very probable that the plant studied by Sienicka is a member of one of the triploid dons. A double-flowered fulvous daylily having variegated foliage was mentioned in the Gardeners' Chronicle in 1864, under the name "H. Kwanso foliis variegatis Possibly the original plants of the so called "H. fulva Kwanso" brought by von Siebold directly from Japan to Europe shortly before 1864 were variegated, for the variegation is evidently of the chimeral type and the plants frequently produce all green branches. The root-tips of several plants of the variegated type have been examined and in these the number of chromosomes is 33. Seedlings of Crosses between Diploids and Triploids The triploid dons Europa and Maculata are evidently fully self and cross-incompatible but they have been used both as seed and as pollen parents in crosses with certain diploids. As a seed parent the Europa Daylily crossed with diploids has given for the plants thus far studied Cytoloeia3.1932 18 254 A. B. STOUT Cytologia 3 five seedlings with somatic number of 22, two with somatic number of 22-23, two •V •V •V 22-24, one •V •V •V •V 26-27, and one •V •V •V •V 21-28.

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