[56] TERATOLOGICAL STUDIES

Transcription

1 [56] TERATOLOGICAL STUDIES I. RECEPTACULAR OUTGROWTHS IN ANTIRRHINUM MAjfUS L. BY B. BARNES, B.Sc, PH.D. (LOND.), F.L.S. Department of Botany, Birkbeck College, University of London (With 6 fiigures in the text) N UMEROUS records exist of abnormal development in Antirrhinum majus, affecting almost all parts of the plant. A stock which has been under observation for the past six years has furnished sporadically examples of many aberrations described by other authors(3, 6, 7, 0), including fusion of the cotyledons and formation of ascidia by them, tricotyly, fasciation of the stems, irregularities in phyllotaxis, feeble attempts at the assumption of a climbing habit (8), peloric flowers, and the occasional production of striped flowers in a raceme mostly consisting of unstdped ones. In 1929, some peculiarities were noted which do not seem to have been described hitherto, as far as can be judged after a survey of the literature available. Three flowers, from two plants, were found to show peculiarities: for convenience of description, these flowers will be referred to as Flowers A, B and C. Both plants were alike in their normal flowers. In these the outside of the tube was dull pink, the front portions of the lips a velvety crimson, and there were two yellow patches on the lower lip. FLOWER A On July 22nd, 1929, during a period of drought, one abnormal flower was found on a self-sown plant, probably from 1928 seed. It was growing on a small rockery, in a soil consisting mainly of old mortar and small stones. The flower occupied the lowest position in a short raceme of eight flowers, and a few small buds. In addition to the abnormal flower, four others were fully open, and were quite normal. Continued observation of the plant, until it ceased to flower in September, showed that no other monstrous flowers formed on it.

2 Teratological Studies 57 Even when fully open. Flower A (Fig. i) was remarkable for its upright posture. It had a single calyx of five sepals, and two corollas. One was of full size, coloured like the ordinary lowers of the plant; it enclosed a normal androecium and gynaeceum. The only abnormality affecting the large corolla was the presence, in the front of the tube near the base, of a hollow, instead of the ridge found in unaltered flowers: the second corolla lay, partly in this hollow, partly in front of it. 5 cm. Fig. I. Flower A. (i) Front view. (2) Side view, (a) Supernumerary corolla, with its pouch (b). The second corolla was composed of an upper and a lower lip, quite separate from one another. The upper lip consisted of a strapshaped portion, partly lying in the hollow of the large corolla, partly emerging from it, and bending forwards and downwards, to end in a wider portion, hollowed internally, and furrowed in such a way as to suggest the presence of two petals. In colour, this lip agreed with the upper lip of a normal flower, but, on its inner surface, just above the beginning of the terminal expansion, lay a thick turf of white hairs like those found on the lower lip of a normal flower, but not usually on the upper lip. This turf was succeeded distally by

3 58 B. BARNES a nearly glabrous region, and then by a longitudinal streak bearing hairs, and corresponding in colour and position to the yellow areas on the lower lip of an unmodified flower. In general coloration, position, and the probability that it consisted of two petals, this lip corresponded with an upper lip; in the hairs, and the yellow streak, it showed characters of a lower lip. It was somewhat deficient in turgor, and weakly built. The lower lip was deeply hollowed internally, and agreed in colour with a normal lower lip. It bore a turf of whitish hairs, followed distally by a transverse series of three, vaguely defined yellow areas, corresponding to the two yellow patches in an ordinary flower. The lip ended in two spreading lateral lobes, separated by a rather wide nick, with a feeble indication of a third lobe in the angle. The outer edges of the lateral lobes were fused with the front edges of the corresponding antero-lateral sepals. In front view, these sepals were hidden by the abnormal corolla, but were clearly visible in side view. Their tips were bent forwards and downwards in the general plane of the sepal, and the whole length of the anterior edge of each sepal was united wdth the neighbouring lobe of the supernumerary corolla. Finally, the base of the lower lip formed a small, wrinkled, double pouch, deep crimson in colour, and protruding between the sepals. The relative sizes of the two corollas are evident from the figure. A median longitudinal section (Fig. 2) did much to clear up the position. The large corolla bore the usual anterior basal pouch, and below this was a small outgrowth from the receptacle, lying in the median plane. The outgrowth gave rise to the two lips of the abnormal corolla, and, in part to the antero-lateral sepals; this explains their union with the second corolla. It was soft and yellow, and contained a weak vascular strand, forking in the middle of the mass. The vascular supply to the second corolla was independent of that to the larger flower as far back as the stalk: beyond that, it was not traced. Sexual organs could not be found in association with the imperfect corolla. It appeared that the unusual condition was due to the formation of an outgrowth from the receptacle, of sufficient strength to allow of an attempt at the formation of a corolla. It is of some interest that both parts of the imperfect corolla, originating from the anterior side of the receptacle of the flower, showed characters of the lower lip of a normal flower. The absence of sexual organs may perhaps be related to the lateral origin of the rudiment.

4 Teratological Studies 59 The second plant On August i6th, 1929, two more abnormal flowers were found at the base of a short raceme of five flowers on a plant growing close to the rockery already mentioned, in soil containing a good deal of limy rubbish. At this time, the dry weather was nearly over. The Fig. 2. Flower A in median longitudinal section: (a) vascular strands; (b) outgrowth from receptacle; (c) white hairs; (d) yellow streak and hairs. corollas were apparently quite normal, and the peculiarities affected in each flower the antero-lateral sepals. During the day, heavj' rain dislodged the corolla of the older flower, but not the sepals; during the next night, the corolla of the second flower fell, and with it, one modified sepal. FLOWER B (Fig. 3) The posterior portion of the left antero-lateral sepal was green, with the usual glandular hairs on the outer surface, and a definite apex. The front edge, however, passed out with sudden change of colour, into a petaloid extension, about half as long again as the sepaline part, and one and a half times as wide. The base of this compound structure was sepaline, distinctly pouched, and arose from a solid and rather massive lateral outgrowth from the receptacle. The tip of the petaline extension turned over towards the outside

5 6o B. BARNES of the flower, forming a bluntly pointed hood, with the curve extending for some distance down the anterior edge; in colour, the extension agreed with the corolla, but bore neither hairs nor yellow patches. Fig. 3. Flower B. (i) Outer face of left antero-lateral sepal. (2) Section along line A-B: (a) apex of sepaline portion; (6) apex of petaline portion. At first sight the right antero-lateral sepal was normal. Inspection showed that it bore a basal swelling, like the one found in Flower C. FLOWER C (Fig. 4) The left antero-lateral sepal closely resembled the corresponding member of Flower B, but was less modified. The hooding of the peta-

6 Teratological Studies 6i line anterior edge lay mostly along tbe side, and the general pigmentation was not so intense as in the other flower. Tbe sepal was not attached to tbe receptacle by an outgrowtb of special character; indeed, tbe attacbment mtist have been weak, as tbe sepal fell witb the corolla, a most unusual occurrcnct-. It bore internally, lying symmetricallv across tbe middle line at the base, a pale yellow kidney-sbaped body, with the conve.xity towards the centre of the flower. This structure was not torn when the sepal 5 mm. Fig. 4. Flower C. (i) Outer face of left antero-latcral sepal. (2) Section along line A-B: (a) apex of scpaline portion; {h) apex of petaline portion; (c) reniform body. came away, and could not have been firmly united witb tbe receptacle. Distally to the reniform body, the inner surface of the sepal bore, on each side of the middle line, and interrupted by it, a pattern of sinuous double red threads lying on a yellowish background; glandular bairs were not present. Further up the inner face, the pattern gave way to a series of longitudinal lines of minute deep red spots, and these passed into a region containing diffuse red anthocyanin. Although a rigid demonstration was not possible, inspection

7 62 B. BARNES suggested that the petaline margin was not a mere lateral extension of the sepal, but that the organ was double in nature, with petaline material in part applied to the inner face of the sepal, in part spreading sideways from it; this was suggested by the distribution of the pigmentation and by the presence of two strong veins. The reniform body was of obscure nature; it seemed to be an outgrowth from the inner face of the sepal, and to have little connection with the receptacle. Externally, the right antero-lateral sepal showed nothing unusual. Internally, it bore at the base, in a position corresponding with the reniform body on the left, a small pad (Fig. 5) of parenchymatous material, yellow below, where there was a smooth bulge, and red 1 mm. Fig. 5. Flower C. Outgrowth at base of right antero-lateral sepal: (a) cut base of sepal and outgrowth, (b) yellow, and (c) red portion of the outgrowth. above, where the surface was irregularly furrowed. The pad had to be cut to detach it from the receptacle of the flower. Sections of this object showed that the pigments lay in the epidermal cells, and that chlorophyll granules were sparingly present in the internal cells; vascular tissue could not be found. The cells of the basal portion were like those forming the mesophyll of the sepal in all but the poverty of chlorophyll, and it was clear that the swelling was an outgrowth from the receptacle. The red portion was of more interest. It consisted of a number of tightly packed lobes (Fig. 6), not arranged in any recognisable order; all contained some red pigment in their epidermal cells. The strongest development of anthocyanin was as

8 Teratological Studies 63 marked as in the distal part of a normal corolla; it was not found until sections were cut, as it occurred in lobes lying deep in the mass. Nothing resembling sexual organs could be found. The inner face of 1 vr\vn. Fig. 6. Flower C. Diagrammatic median lon.tjitudmal section of the outgrowth shown in Fig. 5. The packing of the lobes has been disturbed by cutting. The distribution of the chlorophyll is indicated by the spacing of the lines, that of the anthocyanin by dots, (a) Hair on outer face of the sepal. the sepal was pale yellowish green in colour, and was not in any way abnormal. The remaining sepals of Flowers B and C were examined; they

9 64 B. BARNES were normal. Tin- jjlant was kept under observation until it ceased to flower, but it did not yield any more abnormal flowers. During August and September, over five bundred flowers were examined from plants of the stock: all were perfectly normal. Search was also made at the bases of some bvindreds of fruits formed during the dry weatber, and this also yielded nothing. The abnormal conditions just described cannot therefore be of common occurrence. CON'CLUSIOX Interpretation is bazardous, because of tbe profound modification sbown by tbe parts, and tbe generalised nature of the growths. Tbe unusual conditions all seem to be attributable in the first place to the production of an outgrowth from the receptacle, between calyx and corolla, but not necessarily in tbe axils of the sepals. In Flower A, the outgrowth arose between tbe antero-lateral sepals, and sufficient room was available for tbe development of a recognisable corolla; the sepals were only slightly involved. In Flowers B and C, the left antero-lateral sepals were most strongly affected, and probably had petaline material applied to their inner faces, arising from a skin of receptacle adhering to the base of the sepal. Union between the base of tbe sepal and an outgrowth from tbe receptacle was evident in Flower B, and in both Flowers B and C, unusual pigmentation of the inner face of the left antero-lateral sepal suggested tbe presence of petaline material there. In Flower C, tbe reniform body doubtless corresponded to tbe smootb yellow bases of the swellings associated with the right antero-lateral sepals in both B and C; in the left-hand sepals, the tendency to the production of a petal was expressed in the development of a potaloid extension, but in tbe rigbt-hand sepals this tendency was confined to tbe formation of a deeply coloured and elaborately- lobed upper region on tbe swelling. A complete examination of the vascular system was not made in any of the flowers, but sufficient was done to detect any considerable changes in tbat sj'stem, had such been present; no changes were found, so that the suggested fusion of sepals and extra petals cannot be confirmed by anatomical evidence. It was not known what brougbt about tbe development of the peculiar conditions: the dryness of the season, with prolonged sunshine, and the presence of much lime in the soil, may bear on the matter. Exposure of plants of Antirrhinum to abundant sunlight certainly favours the development of brightly coloured flowers, and therefore of anthocyanin. Bureau (l) found that the peculiar con-

10 Teratological Studies 65 ditions noted in A. majus occurred only on plants growing along a wall facing south: they did not occur on the many other plants in that garden. It is of interest to recall that the first observation of peloric flowers was made by Zioberg, a pupil of Linnaeus (2), in some plants of Linaria vulgaris growing on shingle. In the early autumn of 1915, towards the end of a long spell of hot, dry weather, the present author found many peloric flowers on L. Elatine growing around Vermelles, Pas-de-Calais, where the ground had been thoroughly disturbed by military operations, and much calcareous material brought to the surface. Not far from this spot, at Douvrin, the baron de Melicocq(4, 5) noted many abnormalities in A. majus, some of which, so far as can be estimated by the short notes unaccompanied by figures, were not unlike the modifications described in this communication, but it is not possible to decide if any special conditions affected his plants. The attempts at the adoption of the climbing habit, described by Woodhead and Brierley(8), were first noted in plants growing in a sunny situation, and in soil which had been liberally treated with lime. These observations are suggestive, but they do not justify any definite conclusions: experiment is clearly necessary. The author is greatly indebted to the Department of Botany, British Museum (Natural History), for free access to the extensive literature dealing with the teratology of A. majus. SUMMARY The occurrence in A. majus of extra petals, of petaloid extensions to the sepals, and of pigmented outgrowths at the bases of sepals, is described, and briefly discussed. REFERENCES (1) BUREAU, E. Note sur diverses monstruosites. Bull. Soc. Bot. France, 4, (2) LINNAEUS, C. De Peloria. Upsala, Reprinted in: Amoenitates Academical I (3) MASTERS, M. T.i Vegetable Teratology. London, 1S69. (4) MELICOCQ, BARON DE (LAFONT, A. DE). Monstruosites de VAntirrhinum majus, observ-ees a Douvrin (Pas-de-Calais). Ann. sci. nat. Bot. ser. 2, 16, (5) Monstruosites de VAntirrhinum majus, observees a Douvrin (Pas-de- Calais). Ann. sci. nat. Bot. ser. 2, 5, 61. 1S46. (6) MOQUIN-TANDON, A. Elements de Tiratologie vegetale. Paris, (7) PENZIG, O.'^ Pflanzen-Teratologie, 3. Berhn, (8) WOODHEAD, T. W. and BRIERLEY, M. M. Development of the chmbing habit in Antirrhinum majus. New Phytol. 8, (9) WORSDELL, W. C.I ThePrinciptesof Plant Teratology. London, And literature quoted by the author. PHYT. XXX. I '

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