Fruit Characters in the F2 of a Coprosma Cross.
[Read before the Wellington Branch, 22nd September, 1937; received by the Editor, September 6, 1937; issued separately, June, 1938.]
In two earlier papers (Allan, 1926 and 1929) the first generation arising from the artificial crossing of wild plants (in situ) of Coprosma. propinqua (female) with C. robusta (male) was described, and the vegetative segregation in the second generation discussed. Here is illustrated the remarkable range of fruit colour secured in these plants. For the faithful rendering of the colours, shapes and sizes I am greatly indebted to Miss Eunice Reekie (figs. 1–6).
In the following table are given the statements of Cheeseman (1925) and Oliver (1935) for the fruit characters, together with my own findings for the plants worked with by me.
As to the arrangement of the flowers and fruits the only points of difference are that Cheeseman includes plants with small fascicles in C. propinqua, and that Oliver apparently does not admit solitary flowers in × C. Cunninghamii. Cheeseman did not definitely accept the hybridity of C. Cunninghamii, whereas Oliver does. I agree with Oliver in finding only solitary flowers in true C. propinqua, but have also found solitary flowers to occur both in F1 and F2 of the hybrid progeny. For shapes and sizes of fruits the differences in the three descriptions are not very significant, and do not cover the whole range actually to be found. But while Oliver definitely classes the fruits of C. propinqua as globose, I have rarely seen truly globose fruits in this species, and never as the prevailing shape on any specimen.
While field observations show that in both C. robusta and C. propinqua jordanons with somewhat differently coloured fruits occur, and that the determination of fruit colour is influenced by the stage of maturity the fruits have reached when examined, our findings are in practical agreement for these two species, the two standing markedly apart in fruit colour. With regard to C. Cunninghamii we are distinctly at variance. Comparing this with C. robusta Cheeseman (loc. cit., p. 861) says, “Intermediate states are not uncommon, and are often difficult to place in the absence of fruit.” He thus relies on the “pale and translucent” drupe as the essential point of difference. Oliver (loc. cit., p. 179), recognising unreservedly the hybridity of C. Cunninghamii, and using that name to cover all the hybrid forms (i.e., not using the name in the restricted sense that Cheeseman adopts) states: “The fruit is globose or oblong and translucent, thus lacking both the red colour of C. robusta and the blue of C. propinqua.”
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Cheeseman||Oliver||Allan||Cheeseman||Oliver||Allan||Cheeseman||Oliver||Allan for F1|
|Arrangement||dense peduncled glomerules||compound peduncled clusters||compound peduncled clusters||solitary, or 2–4 flowered fascicles||solitary||solitary||in 3–12 flowered glomerules||as in robusta, but fewer per cluster||solitary or in 2–5 flowered clusters|
|Colour||yellowishor orange-red||dark orange-red||scarlet||bluish or bluish-black or black||pale blue speckled with dark blue||bluish-black with small semi-translucent patches speckled blue||pale and translucent||translucent||mostly pale and semi-translucent with few blue specks|
|Shape||oblong to ovoid||oblong or narrowly ovate||oblong-elliptic in outline||globose or broadly oblong||globose||subglobose to broadly oblong-elliptic in outline||broadly oblong||globose or oblong||broadly oblong-elliptic in outline to subglobose|
|Size||¼ to ⅓ in. long||8–9 mm. long, 4–5 mm. broad||8–9 mm. long, 4–5 mm. broad||⅓ in. long||7 mm. diam.||6–7 mm, long, 4–5 mm. broad||¼ in. long||5–6 mm. long, 4 mm. broad|
Fruit colour in the F1 females raised by me was described (Allan, loc. cit., 1929, p. 335) as follows: “On most plants the fruits were pale and translucent, with few or no purple flecks, thus matching the description of Cheeseman (Manual N.Z. Flora, 1925, p. 861) for C. Cunninghamii; on others they had more purple and approached those of C. propinqua, while on a few they were yellowish, and on one almost orange, thus approaching C. robusta.”
My second generation flowered and fruited abundantly in 1934 and subsequent years. Of the 54 plants 26 proved to be female. No one plant had exactly the same fruit colour as another. On the basis of the charts published by the Société Francaise des Chrysanthé-mistes (1905), the ground colours may be approximately grouped as varying shades of: milk-white, yellowish white, greenish white, sulphur-yellow, buttercup-yellow, yolk-yellow, chrome yellow, Indian yellow, scarlet orange, red orange, and tomato-red. In all but the scarlets and reds, and even faintly in some of these, there was more or less spotting with cornflower to prussian blue, and in one or two examples the main colouring was a deep prussian blue. Fruits with the very pale colours were semi-translucent.
The arrangement graded from solitary fruits to rather large, dense, compound clusters. The shapes covered those of the parent species and were fairly constant for any one plant, while there was the same range of size. The number of plants available is too small to justify any attempt at detailed factorial analysis, but there appears to be a distinct tendency for greater leaf-size to be associated with greater degree of clustering, and a rather less-marked tendency for the clustering to be associated with the red colour derived from C. robusta. Fruit-size and shape apparently segregate independently of fruit colour. Cockayne and Allan (in Cockayne and Turner, 1928, p. 142) suggested the name × C. prorobusta for the whole group of hybrids found in nature between the two species, and the restriction of the name × C. Cunninghamii to those forms closely approximating to the original description of Hooker. Oliver (loc. cit., p. 179) uses × C. Cunninghamii for the whole group, treating the name × C. prorobusta as a synonym. The point is perhaps of no great importance, but if the name × C. Cunninghamii be adopted for the whole group, the second generation here described shows that Oliver's statement as to fruit colour cannot be retained. Of wild hybrids, too, the most that can be said is that pale semi-translucent drupes, possibly mainly on F1 plants, appear to be more plentiful than the more highly coloured ones.
Allan, H. H., 1926. The F1 progeny resulting from the crossing of Coproama propinqua ♀ with C. robusta ♂, Genetica, VIII, pp. 155–160.
— 1929. The F2, progeny resulting from the crossing of Coprosma propinqua ♀ with C. robusta ♂, Genetica, XI, pp. 335–346.
Cheeseman. T. F. 1925. Manual of the New Zealand Flora, ed. 2. Wellington.
Cockayne, L., and Turner, E. P., 1928. The Trees of New Zealand. Wellington.
Oliver, W. R. B., 1935. The Genus Coprosma. Bernice P. Bishop Mus. Bull., 132.
Sociěté Francaise des Chrysanthémistes, 1905. Répertoire de Couleurs.
Legend of Illustrations.
Figs. 1–6.—Fruit colour in F2 Coprosma hybrids. Drawn by E. Reekie.