Some Points in the Morphology of the Stipules in the Stellatae, with special reference to Galium

Abstract

With twenty-seven Figures in the Text I T is hardly necessary to recapitulate here the results of the previous investigators on the nature of the leaf-like organs or ' leaves' in the apparent whorls of Galium, and of many other members of the Stellatae (or Galieae, a tribe of the Rubiaceae). There is little doubt that in any whorl the two opposite ' leaves', one at any rate of which subtends an axillary shoot, are the true leaves, while the other members at the same node are stipules. Thus, in the case of a six-membered whorl there are two leaves, each of which is provided with two stipules. Where only five or four ' leaves ' occur in a whorl, it is usually understood that in the first case one, and in the second case both, pairs of stipules have undergone a concrescence. If, however, more than six ' leaves ' are present in a whorl, it is explained that one or more of the original four stipules have undergone chorisis, resulting in the production of supernumerary members. 1 Eichler found in Galium Mollugo and also Rubia tinctorum, that there are often two primordia which fuse, giving rise to a single interfoliar stipule on either side of the stem. 2 Goebcl, 3 on the other hand, found in

Molecular systematics of tribe Rubieae (Rubiaceae): Evolution of major clades, development of leaf–like whorls, and biogeography

“…Subsequent expansion of the interpetiolar stipules produces whorls with greater than four leaf-like organs (Robbrecht, 1988). This hypothesis of whorl development coincides with Takeda's original idea that whorls of six leaf-like organs have been derived from a four-organ whorl (Takeda, 1916). Cronquist (1968) also hypothesized that six or eight organs at a node were derived from species with four-organ whorls, but did not provide a detailed description of this change.…”

“…However, whorls within Rubieae vary with respect to number of leaf-like organs, from four to twelve or more. This variation is interpreted as due to fusion or fission of stipular organs (Takeda, 1916). Recent SEM studies do not show any evidence of fusion of stipules during development (Rutishauser, structure on either side of the stem.…”

“…However, the presence of four or more leaf-like organs at a node differentiate Rubieae as having "leaf-like whorls". The development of leaflike whorls in Rubieae has been hypothesized as originating from a pair of opposite leaves and associated, independent leaflike stipules (Takeda, 1916). This hypothesis has been supported by the observation that only two leaves in a whorl are associated with axillary buds and obtain their vasculature from the stele, whereas leaf-like stipules obtain their vasculature from girdling leaf traces (Rutishauser, 1999).…”

Geometrical relationships specifying the phyllotactic pattern of aquatic plants

“…For example, the dicot Galium rubioides (Fig. 6E) produces a whorl of leaflike structures that consists of two leaves and 4-6 stipules that are transformed into leaflike organs (Takeda, 1916;Troll, 1943). Although Rutishauser (1984) argues that these modified stipules are genuine foliage leaves, the weight of morphological evidence, such as the absence of associated buds, discloses their stipular nature.…”

Polymerous Leaf Whorls in Vascular Plants: Developmental Morphology and Fuzziness of Organ Identities

“…Rubieae such as Galium palustre and Rubia peregrina oscillate between four and five leaves in successive whorls. This instability in phyllotaxis is combined with an increased tendency to form forked (two-tipped) Pleaves (Takeda 1916;Troll 1939). Forked leaves are rare in Rubieae with constant leaf number, e.g., in the regularly tetramerous whorls of Galium boreale.…”