A Clear Case of Periclinal Chimera

BIZZARRIA--A CLEAR CASE OF PERICLINAL CHIMERA. B• TYOZABUR0 TANAKA. P hytotechnicaI I nstitute, M iyazaki C oUege of A gricultur e, M iyazaki, J apa~ . (Cont¡ No. 10.) (With Three Plates.) THE bizzarria orange is generally referred to as the typical illustration of a seetorial chimera. Early accounts of Nati(15) and others following hito accredit its o¡ to a defective grafting between citron (Citrus medica Linn.) and sour orange (Citrus Aurantium Linn.), accidentally obtained by a Florentine gardener in 1644. Anillustration of Risso and Poiteau(21), later copied by Engler and Prantl(9), strongly suggests a secto¡ character. Fuller accounts of its origin and eriticism of its natu~e were given by Gallesio (1% Darwin(s), and Penzig (17), (18), but time was premature for these authors to ar¡ at any satisfactory conclusion. Strasburger(~), discussing from bis cytological study of the vegetative sphere of citron, sour orange and bizzarria, concluded that the bizzarria cannot be a case of somatic hybrid but possibly is a sexual hyb¡ though there is no proof of ir on record. Winkler's(2s) discovery of plant chimeras caused by grafting, eventuaUy made Strasburger change bis opinion, and he(24) suggested the possibihty of the existenee of "hyperchimera" in plants, presenting bizzar¡ asa possible case of ir. Baur(% from bis studies on the variegated Pelargonium, advanced the opinion that plant chimeras ate divisible into two classes, sectorial and periclinal. Winkler(S9), and Buder(5), using the terminology of Baur, classed aH of the tomato- nightshade graft-hyb¡ as perichnal chimeras, with the exeeption of Solanum Darwinianum, which W]nlder classed as "Verschmelzungs- Pfropfbastard." lqeither Winkler nor Baur made mention of bizzarria, but since Baur(s) maintains that hyperchimera is in anatomical con- struetion simply a perielinal chimera, bizzarria, according to bis defln~- tion, may be classed as a periclinal chimera. This deduction, however, failed to attract the attention of succeeding w¡ Goldschmidt(u) was probably the first author to cite bizzarria as an undoubted case of secto¡ chimera, and the unfortunate coincidence of Haecker's book(12) appearing almost at the same time created 78 Bizzaria--a Clear Case of Periclinal Chimera a wide acceptance for this assumption. Together with the misleading Risso-Engler illustration of bizzarria, many textbooks copied the infer- ence as ah example of the rather rare occurrence of sectorial chimera in the plant kingdom. Later w¡ as in the cases of Plate (19), Molisch (14), and Babcock and Clausen(1), seem to tend to recognize the partial occurrence of pe¡ formation of the fruit, but no critical statement is presented. Careful reading of the anatomical account given by Stras- burger(~3) will show that the occurrence of seetors of bot/citron and sour orange flesh within a single fruit is exceptional, and his statement is too unconvincing to warrant the acceptanee it reeeived. Risso and Poiteau (21) state that the citron character does not affect the sour orange centre, or penetrate as far as its axis, but their painting shows that the bizzarre outline does not affect the citron centre. An exactly similar nature of the pulp is later exhibited by the drawing of Poiteau and Turpin (~0). In the winter of 1922-1923, the writer made a critieal study of the bizzarria plants at Florence and La Mortola, through the courtesy of the Botanical Institute of the University of Florence and the Giardino Hanbury of La Mortola near Ventimiglia, Italy. Some potted plants in the greenhouse of the former, labelled bizzarria, were found to be normal sour orange, while some others bore binary oranges. None was the typical bizzarria fruit as so excellently illustratcd by Poiteau and Turpin(2o~. In the field of La Mortola garden, a plant presented a very typical bizzarria, bearing a fine bifacial fruit which was later submitted to the examination of the w¡ This particular fruit is described below (Plate VI). Fruit medium in size, 19.6 cm. in girth, 6.3 x 6.1 cm. in diameter, and 5.8 cm. high, longitudinally divided into part sour orange and -~- part citron. Sour orange part oblate, about 5"5 cm. across and 4.2 cm. high, apex rounded, slightly depressed toward the stylar point, base much depressed to the calyx; surface even, indistinctly very fine streaked, finely pitted with rather indistŸ oil cell dots; colour gTeen, beginniug to change into orange; the peel breaking longitudŸ at one point, disclosing more or less sunken citron-like surface, the striations becoming more distinct at the stylar end. Citron part very rough, irregularly tuberose, longitudinally streaked, striations irregular, branching, deeper coloured, showing at one place clearly the texture and colour of sour orange; colour of peel pinard yellow to light cadmium (Ridgway, Color Standard, Plate IV), oil cell dots far apart, size uniform, shallowly con- cave, distribution irregular. Calyx flat, very irregxfiarly lobed, oil cell dots indistinct but projecting like warts; texture thick, glabrous. T:162 TANAKA 79 Section periclinal, normal citron pulp enclosed in a sour orange peel, the latter being partly penetrated by citron charaeter. Sour orange rind thick, 9-11 mm., coloured, with imbedded fibres; oil cells close, fine, oblong, homogeneous in size bt~t arranged in irregular rows; inner layer containing several fissures forming empty holes. Citron rind distinetly separate Ÿ the former, conneeting at a certain place with the pulp ball, pure white, about 20 mm. thick, texture solid, no imbedded fibres, oil cells large, oblong, distant, outline not definite, arranged in different depths, some reaehing lar interior, very light greenish yellow. Pulp ball small, round; segments 11, regular; outer end rounded, inaer end obtuse; central column large, 10 • 6 mm., solid, fibre strands circinate, not prominent; segment watl thick, holding white pith between. Pulp white, solid, transparent, acid, vesicles elongated, parallel, very few in number, flexible. Seeds few, small, plump, smooth, rosy outside, testa thin, tegmen beautiful rosy purple, contaiuing white mono-embryo. The La Mortola plant is a dwarf tree about one metre in hcight with a single main trunk inclining toward north-east. The plant bears three distinct kinds of foliage; namely, typical sour orange leaves, typical citron leaves and typical bizzarria leaves as painted by Risso and Poiteau(21). The sour orange leaves ate charaeterized by a thick, deep green blade and definitely winged petiole. The citron leaves ate oblong, lighter coloured, much thinner, distinctly serrate on margin, and devoid of petiole wing. The bizzarria leaves in general resemble the sour orange leaves, but are quite irregular in outline and variable in shape. They ate occasionally very mueh narrowed and boat-shaped, and are some- times more or less variegated. Ah abnormal linear forro markedly tapering at both ends is also found. The petiole wing is quite va¡ ranging Irom linear to oboval. The first horizontal branch of the La Mogola plant comes out quite near to the gro .und, stretching toward the north-east, and bears typical bizzarria shoot at the terminal (Plate IV, C). A side branch, eoming upward about the middle of this branch, shows typical eitron leaves at the tip (Plate IV, A). The second braneh, starting from the trun~ about 7 cm. above the ground, rises southward with rather strong inclination, 67 cm. in total length. Two fruits are borne on this branch, the terminal one being the one described above. The second fruit, not taken for study, is also bizzarria, appearing like an immature warty eitron with deep green soar orange streaks. The foliage below these fruits presents normal bizzarria characteristics. Nearly all of the side branches of this second branch have bizzarria characteristics, exeept two small citron shoots rising about the middle of the second side branch, and the 80 BizzarŸ Clear Case of Periclinal Chimera sour orange terminal shoots of the first side branch. The latter is a very remarkable case of the segregation of very stable sour orange from rather variable bizzarria, the demarcation being so clear that ir looks as Lf two different kinds of shoots were graŸ together. The bizzarria foliage below the joint is particularly small, narrow and acutely tapering, while sour orange leaves attached are large, oval, well spreading and widely alate. The writer(25), (~6),(27) has been studying many remarkable cases of bud variation and vegetative reversion between "Wase" (praecox) and normal characters in Satsuma orange (Citrus unshiu Hort.), but he has never observed such remarkable segregation on a single growing axis. From the joint of this second branch, the main trunk rises obliquely fora distance of 14 cm. with inclination toward the north-east, and there forks into two large spreading branches, leaving a slender straight shoot ascending in the opposite direction from the main trunk. The forking branches again fork almost alike on the two sides and are all typical sour orange, none bearing bizzarria foliage, while the slender one is bizzarria throughout. In this case segregation must have taken place at the point where the trunk made the first forking. The specimen of sour orange leaves (Plate IV, B) was taken from the second branchlet from the north. The plantas a whole is a bizzarria with large fan-shaped top of segre- gated sour orange, and with occasional reversion to both sour orange and citron. The tree is trifacial in nature just exactly like CrataegomesTilus Dardarii, a pIant of which was studied by the writer with the kind aid of Prof. W. Johannsen of the University of Copenhagen. This Bronvaux medlar regularly sends forth two kinds of reverted shoots, i.e. pure medlar and pure whitethorn, so that three kinds of branches are present on the same tree, justas in the case of the bizzarria orange here described.

Load more