Yoshitaka Imai

Geno- and plasmotypes of variegated pelargoniums

ConclusionVariegated and periclinal pelargoniums offer some very puzzling problems. Chittenden (1927) collected some of these cases, which, however, have become simplified as the result of my investigations. Two forms of variegation were identified, the one due to sorting out of mixed plastids, and the other to recurrent exomutation of plastids induced by a recessive stimulant gene that is mutable itself. Various plasmotypes of plastids differ in their colour, the degree of crumpling of tissues, and mutability. The plasmotypic change of plastids is either automutable or exomutable, while sometimes the plastids transform in two directions. The white-over-green periclinals generally have albinotic epidermis. In the majority of cases unstable chlorophyll periclinal types change into stable types, probably at the growing points. Freak of Nature, Chittenden’s variety A, and the green crêpe sport from Hanamikado are periclinals with differentiated ectohistogens, it being green in the first named and albinotic in others. The extent to which the respective three histogens contribute to the ontogeny of the plant body is considered from both anatomical and genetic investigations. Since in leaf formation of the pelargonium the ectohistogen develops into the marginal mesophyll as well as the epidermis, the mesohistogen into the outer and submarginal mesophyll, and the endohistogen into the innermost mesophyll, the chlorophyll periclinals with differentiated ectohistogens bear leaves with margins of a different colour.

An apparently simple inheritance of variegation inPolygonum orientale

ConclusionThe variegated form ofPolygonum orientale L. is outwardly simple recessive to self-green in inheritance, but its white patches and branchlets are products of the exo-mutations of green plastids, which are mutating frequently to white owing to the action of a recessive stimulating gene carried by the stock. The albinotic seedlings, which might be expected from the achenes of the variegated plants as well as those collected on the white branches, are not obtainable, because the fruits do not germinate. This fact eliminates the possible production of albinotic seedlings, and simplifies the segregation of the variegated form in its inheritance.This plant seems to be a di-histogenic dicotyledon, whose general plant body is possibly derived from two histogens, while its stipules are from the outer histogen only.I am of the opinion that, in view of the foregoing remarks concerningPolygonum, some cases of other plants that have been reported as being Mendelian in inheritance, should be checked by experiments.

The Mechanism of Bud Variation

DARWIN (1882) first called general attention to the significance of bud variation. Since then many observations have been recorded in the literature of the subject (cf. Cramer, 1907). Bud variation frequently plays an important role in practical science. One of the most laborious studies in this field was made with Citrus, particularly the data collected by Shamel and his collaborators in America, and by Tanaka in Japan (cf. Tanaka, 1932). The mechanism of bud variation is based on Baurs theory of periclinal chimeras (1909), which was supported and extended by later investigators, especially Krumbholz (1925), Chittenden (1927), Lange (1927), Massey (1928), Imai (1931) and others. Noack (1922) and others, however, opposed it, suggesting in its place the theory of somatic segregation, but this view runs counter to the general genetic evidences. Recently, the idea of mutable genes has aided greatly in a clear understanding of the mechanism of bud variation (Imai, 1934).

Linkage Studies in PHARBITIS NIL. I.

SummarySo far the loci determined inPharbitis Nil number 72, being located in 12 chromosomes. They include the two newly approtioned genes dwarf (dw) of the delicate linkage group and Globose (Gb) of the cordate linkage group. The recombination frequency is 30.3 per cent for dwarf and delicate and 4.9 per cent for Globose and cordate.Globose is qualified by the two recessive genes, no-lobe (nl) and no-lobe-suppressed (nl-s).

The structure ofAlbomargin ata andMedioalbinata forms

SummaryFrom both experiment and theory, our knowledge of the structure of thepseudo-medioalbinata, albomarginata, andmedioalbinata leaves may be summarised as follows:1.Thepseudo-medioalbinata form is a green-over-white periclinal, modified secondarily by the influence of the albinotic endohistogen. Its progeny therefore are all green. Root cuttings may give rise to albinotic shoots.2.Thealbomarginata form is a periclinal with white ectohistogen in dihistogenic plants. In these plants, the ectohistogen develops into the epidermis and the marginal mesophyll of leaves, while the endohistogen constitutes the other inner components. The white-fringed leaves of such trihistogenic dicotyledons asDaphne andFragaria are due to the development of the white ectohistogen that forms the epidermis and the fringed mesophyll of the leaves.3.Themedioalbinata form, which occurs in some monocotyledons, is due to the green-over-white arrangement of the two histogens.

The types of spotting in mice and their genetic behaviour

Summary1.The results reported in this paper agree in the main with those of Little and Detlefsen. More experimental evidence, however, is supplied by the present investigation.2.In the present studies, however, the dominant spotting of the “Kasuri” race was distinguished and separately recorded from the recessive ordinary spotting, so the comparison between observation and expectation was more closely dealt with.3.The D factor acting upon S, the factor for self, in somewhat restricted fashion on the development of the coat-colour results in the “Kasuri” pattern, and the same factor working upon S’, a factor for the spotting, results in a dark-eyed white of the “Daruma” type.4.On the one hand the D factor acts as dominant upon the pattern development as was stated above, and on the other hand it works recessively in regard to the lethal effect. Mice homozygous for this factor perish in the early ontogeny whether they have S or S’ as the hypostatic factors.5.The “Kasuri” race often become sterile, especially on the female side. This condition was also found to occur in the “Daruma” race in a few instances.

On a monstrous flower and its linkage in the Japanese morning glory

Summary1.The heart leaf (h) and the “Shishi” form (si) are respectively transmitted as recessives to the normal.2.Owing to the incomplete dominance of the H and Si factors the segregating ratios are each a 1 : 2 : 1.3.About 1.2 per cent. of crossover occurs in a linkage between these two factors. By the convenient nature of incomplete dominance calculation of. linkage was directly made with the self-propagated specimens in the hybrid progeny.4.The percentage of crossover is almost equal in the case both of coupling and repulsion.5.The Si factor represents multiple effects on flower and leaf as well as cotyledon.6.The grasped leaf found in the “Shishi” strain is due to the result of the additional effect of a punched factor (u).

Variegated flowers and their derivatives by bud variation

SummaryThe anthocyanin variegation due to mutable genes gives bud variation in accordance with a definite mechanism of ontogeny. In the variegated azaleas, bud variations occur in various directions, including those to the ground colour. These sports can be explained by recurrent mutation, and sometimes by somatic rearrangement of tissues. The fringed flowers ofRhododendron, Punica, Chaenomeles, andCamellia are regarded as periclinals with mutated, self-coloured meso-histogens. In certain other plants however fringing does not appear in similar periclinals, owing to differences in the extent of development of the ecto-histogen in corolla ontogeny. Sometimes the mutated or the genotypically different mesohistogen does not affect the flower colour or coloration, because the tissues do not contain any pigment.

Maternal Transmission of Mutated Plastids in the Japanese Morning Glory

Chlorophyll variegation, which is commonly found in the Japanese morning glory (Pharbitis nil), is transmitted as a simple recessive to the self-green condition. The whitish patches appear somewhat irregularly on the respective leaves of variegated individuals, so that the variegation is regarded as a pattern character. The allelomorphs, normal (self-green) and variegated, are quite constant and no cases of mutations either from normal to variegated or its reverse have come under our notice. In I928 three unexpected variants with variegated leaves incidentally occurred in the hybrid progeny of different crosses, their sister plants being invariably self-green. The variegation of these plants differed in color, namely: I. White; variegation in white. 2. Creamish; at first cream in color and creamish white in the extended leaves. 3. Yellowish; variegated with yellowish color, a little more intense in the young leaves. The white-variegated variant puts out at times green and white branches (fig. I) and also chimerical bud variations with periclinal white-over-green tissues. The results obtained from selfing the flowers of these branches are collected in table I. The albinotic seedlings had short hypocotyls with small cotyledons and perished about two weeks after germination. The green individuals thus segregated bred true to type for generations, while the variegated ones gave rise to three forms in various proportions according to the amount of variegation of the mother plants or of the branches from which the seeds were collected. The slightly variegated branches or individuals gave mostly green seedlings, whereas the highly variegated ones produced mostly albinotic seed-

The mechanism of variegation inPlantago andCapsicum

SummaryThe variegations seen inPlantago andCapsicum behave as recessives to normal green, but their true genetic nature is complicated. The white patches in the variegated leaves have green ticks. The mechanism involved in variegation consists in white patches resulting through exomutation of the green plastogene, and in green ticks by automutation of the white mutant plastogene. Almost white sports and white-over-green periclinal sports appear. In the course of sexual reproduction, retroversion to the apparently green condition takes place, so that white and periclinal branches or ears generally produce variegated seedlings.