COMPARATIVE MORPHOLOGY OF THE CARPEL IN THE ROSACEAE VII. POMOIDEAE: CHAENOMELES, CYDONIA, DOCYNIA

The multi-ovulate pomoids, Chaenomeles, Cydonia, and Docynia, all have closed sutures and extensive fusion between carpel and floral cup and between ovular and wing bundles. Although the ovules in Docynia are generally apotropic and few in number (4-7), the ovules in the other two genera are pleurotropic and numerous (15-48). A statistical treatment of the whole tribe of Pomoideae shows that in carpels with open sutures ovular and wing bundles definitely tend to be separate while in those with closed sutures these bundles tend to be fused. To a lesser degree carpels with open sutures also tend to have bitegmic ovules, separate carpels, and a lesser extent of fusion between carpel and floral cup, while carpels with closed sutures tend to have monotegmic ovules, united carpels, and a greater extent of fusion between carpel and floral cup. THE POMOID genera, Chaenomeles, Cydonia, and Docynia, have multi-ovulate carpels. In 1906 Schneider described the genus Pseudocydonia. Weber (1964) believed, however, that this taxon is really Cydonia and that Pseudocydonia sinensis Schneid. is more properly named Cydonia sinensis (Dum.-Cours.) Thouin. If it be considered that the multi-ovulate condition is atavistic (Bailey and Swamy, 1951; Eames, 1961), the carpels in this group could be expected to show other primitive features. It is with considerable interest, then, that an analysis of the multi-ovulate genera has been undertaken. MATERIALS AND METHODS-Flowers for this study were generously provided by the Miorris Arboretum, the Arnold Arboretum, the U. S. National Herbarium, the Harvard University Herbarium, and the herbaria of the Natural History Museum of Vienna, the University of Vienna, and the University of California (Davis, Berkeley). The species studied, with the number of samples indicated in parentheses, incluide Chaenomeles cathayensis (Hemsl.) Rehd. (1), C. japonica (Thunb.) Lindl. (3), C. speciosa (Sweet) Nakai [C. lagenaria (Loisel) Koidzuml (2); Cydonia japonica Lindl. (2), C. oblonga Mill. (2), C. sinensis (Dum.-Cours.) Thouin (6), C. vularis Pers. (4); Docynia delavayi Schneid. (2), D. docynoides (Schneid.) Rehd. (2), D. indica Decne. (2), D. rufifolia (Ldveill6) Rehd. (1). Specimens were prepared in the manner previously described (Sterling, 1964a). As in previous studies (see Sterling, 1964c) the observer follows the course of the vascular bundles, as they appear to ascend from the receptacle. No ontogenetic movements are implied in the de'Received for-publication February 9, 1965. This study wasi supported by grant G-16142 fr om the National Science Foundation and by a fellowship grant t_ _-,_h Tr_hr_ CMna_ 17_1-___1nhoim V_-_AlW ilfSi.ir4scriptive terminology, which has been chosen mainly for convenience. RESULTS-Chaenomeles-A set of dorsal collateral bundles, equal in number to the number of carpels (4-5), is separated from the gynoecial cylinder in the receptacle. The remaining bundles of the cylinder, which are normally oriented, lie grouped closely together in a like number of arcs. These arcs are convex centripetally at the base of the locules and alternate with the locules and the dorsal bundles (Fig. 1). The arcs become Vshaped higher up, with the vertices directed centripetally. Each divides radially at the vertex of the V. The division takes place just below the locule in C. cathayensis and above the locular base but below the lowermost insertion region in the other two species. Two large ventral bundles are thus formed, each supplying one of two adjoining carpels above and furnishing branches to the ovules. With reference to the receptacle, the ventral bundle has centripetal xylem and centrifugal phloem when first delimited. Below the lowermost insertion region in C. cathayensis, but above this region in the other two species, the ventral bundle rotates and becomes V-shaped with the vertex centripetal. It then divides radially into a wing bundle that lies near the carpel margin and a large ovular bundle complex near the suture (Fig. 3). These bundle groups are oriented so that the median longitudinal planes of the two derivatives are near-tangential, the phloem of the wing bundle facing the lateral carpellary margin and the phloem of the ovular bundle complex facing the suture. The ovu]ar bundle complex consists of two or three nearly distinct bundles, the innermost one (i.e., closest to the funiculi) giving rise to a branch to each ovule along a carpellary margin. Along its upper course the ovular bundle complex becomes more and more attenuated. It disannears