Mirabilis jalapa, commonly known as ((Four O'clock"' "Sweet Marvel of Peru," or '(Printoponite," belongs to the Nyctaginaceae. This species is cultivated for the brilliant color and pleasing odor of its flowers. Due to its simplicity, the breeding behavior of the self flower colors has furnished classical material for illustrating the simple laws of inheritance. It may be shown, however, that the breeding behavior of these self flower colors is not so simple as was first implied, and that where formerly there were only a few flower-color classes recognized, now there are many. CORRENS (1902,1904), the first to investigate this species genetically, failed in many cases to recognize and classify the flower colors correctly. His attention was chiefly directed toward an interpretation of the "yellow X white" varietal cross in which reds (red being used in a very general sense to cover a number of different shades) were obtained in the F1 and F,, but he failed to distinguish between the F, red flower-color types. The careful distinction between the color classes came with the work of MARRYAT (1909). Aided by the discovery of "recessive white" (MARRYAT'S W7), she was able to detect the genotypes of all the material used in her investigations. The "rose pink" homozygote and "light pink" heterozygote of KIERNAN and WHITE (1926) were probably the first true pinks known to genetic literature on this species. The pink so frequently referred to in text-book illustrations as resulting from a "red X white" four o'clock cross is probably not pink, but magenta (see also MARRYAT 1909, andKIERNAN andWHITE 1926).M . jalapa was introduced into Europe by the Spaniards in 1596. I t is native to Peru, as one of its common names, "Sweet Marvel of Peru," suggests. HEIMERL (1901) found it to be native also to northern Mexico and the southern boundary of the United States. Under cultivation color varieties not known to the wild condition have occurred, and are recurring, spontaneously. MATERIALS AND METHODSThis investigation (1) reviews all crosses, and reciprocals, previously made with true-breeding self flower-color varieties of M . jalapa;(2) attempts to describe the breeding behavior of Flesh Pink and Light Rosaline Purple, two new true-breeding types which have been found during the
The genus Mirabilis has attracted only slight attention cytologically. Hofmeister (1858) briefly described the structure of the tapetum in Mirabilis jalapa. Tischler (1908Tischler ( , 1929 described pollen development and gave chromosome counts for M. longiflora (see Gaiser, 1930), M. jalapa, M. tubiflora, and the hybrid, M. jalapa X M. tubiflora.. Roten (1927), in an embryological study of the Centrosperms, makes frequent reference to features in the micro-and megasporogenesis of M. jalapa. A thorough study of meiosis in a related form, Buginvillaea glabra, has been made by Cooper (1931).The present problem arose while attempting a genetic analysis of certain members of the genus Mirabilis, without evaluating its merits as cytological material. For the most part it is cytologically as undesirable as it is genetically superb for study. The chromosomes are small and numerous, the amount of spore tissue is small, and the time during which reduction division figures may be obtained is short. However, other features treated below, coupled with the meagre knowledge of its cytology, recommend the genus for study. MATERIALS AND . PURPOSEThe present investigation began in 1930. Three species of Mirabilis and one species hybrid have been used in this study-namely, Mirabilis jalapa L.; Mirabilis longifiora L., Mirabilis multiflora Gray, and the hybrid, M. jalapa X M. longiflora. In obtaining the hybrid, M. jalapa was used as the female and M. longiflora as the male parent. The reciprocal of this cross could not be effected (see also Kolreuter [Roberts, 1929], and Correns, 1902). The hybrid is larger than either of the parent types, and is more resistant to cold. Only a small percentage of its flowers set seed. M. multiflora was studied for chromosome counts only.This investigation attempts (I) to make a comparative study of the chief features of microsporogenesis in these materials, (2) to determine the chromosome numbers of the species and hybrid, and (3) to determine the cause, if possible, of degenerating microsporocytes and microspores.To obtain proper division figures of the material, it was necessary to collect the buds at intervals over a period of approximately two and onehalf hours prior to and one-half hour after the time of anthesis in the mature buds. In the middle of July anthesis takes place about 6 p.m. at The 0594
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