The unusual ramification mode of Sphaerothylax abyssinica (Wedd.) Warm. (Podostemaceae - Podostemoideae)

Structural analysis of the dissected ensiform leaves and shoot morphology of Marathrum foeniculaceum (Podostemaceae)

“…As observed in Podostemoideae so far, e.g. in Zeylanidium subulatum (as Podostemum subulatum), Z. munnarense (as Podostemum munnarense), Sphaerothylax abyssinica, Maferria indica (Ja¨ger-Zu¨rn, 1999, 2000b, c, 2002b, the original leaf margins combine at the sheath tip, disappear or become indistinct. The adaxial (''ventral'') side of the leaf between the margins of the sheath becomes indistinct while the morphologically abaxial side of the leaf prevails.…”

The ramification of Apinagia riedelii: A key to the understanding of the plant architecture of Podostemaceae, subfamily Podostemoideae

“…Their absence has caused confusion. The view of the non-axillary or subfoliar position of branches projecting from the lower side of the dithecous leaf has resulted in several misinterpretations (Ameka et al, 2002;Imaichi et al, 2005;Jäger-Zürn, 2000;Moline et al, 2006;Rutishauser, 1997;Rutishauser et al, 2003;Warming, 1888, p. 49). These interpretations are based on the assumption that the dithecous leaf is the structure that ''subtends'' the branch, and the branch meristem is thus an unusual kind of axillary meristem of the dithecous leaf.…”

“…8). And third, the branch bud, therefore, automatically becomes positioned ''within'' the leaf as seen in Sphaerothylax abyssinica (Jäger-Zürn, 2000) and other examples (Jäger-Zürn, 1999). It makes sense to consider the ventral (not the dorsal) side of the dithecous leaf as the sheath that develops a protecting cover around the flower bud, even in the form of an ochrea.…”

“…Ramification of many species of subfamily Podostemoideae deviates from the typical pattern of angiosperms, since branches arise below instead of above the leaf that is associated with branching (Jäger-Zürn, 1999, 2000, 2005aJäger-Zürn et al, 2008). The associated leaf is called ''dithecous'' (Warming, 1888) because it has two sheaths on the lower leaf zone, i.e., one each on the adaxial and abaxial sides.…”

The shoot apex of Podostemaceae: De novo structure or reduction of the conventional type?

“…The view of the floriferous shoot arising from the base of a (dithecous) leaf, corresponds to the concept of a ''daughter leaf'' (Rutishauser, 1997). The ramification mode stated by Imaichi et al (2005) becomes, however, rather confused in extended cymose inflorescences of Z. subulatum with two leaves instead of one, especially if occurring in the form of a rhipidium (helicoid cyme) in Z. subulatum (Ja¨ger-Zu¨rn, 1999, p. 313), as well as in the repeatedly sympodially branched cymose inflorescences of other Podostemoideae (Sphaerothylax abyssinica, Maferria indica, Podostemum weddellianum, Apinagia multibranchiata, A. latifolia and Marathrum foeniculaceum (Ja¨ger-Zu¨rn, 1997, 1999, 2000b, 2002a, b, 2005b. Before unanimous acceptance, the proposal of the origin of a (leaf-borne) shoot (i.e., a branch) instead of an (adventitious) leaf must be thoroughly substantiated by more investigations.…”