The Architecture of Inflorescences in the Myrtales

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Abstract
In the Myrtales a great variety of inflorescences are found. In some families such as Oliniaceae or Alzateaceae (formely included into Lythraceae) the inflorescence are exclusively of the more primitive monotelic type. In others gradual transitions from the monotelic to the polytelic type can be observed. Within the Lythraceae the genera Lawsonia, Lagerstroemia, and Galpinia and.sbd.if included as subfamilies.sbd.the Punicoideae and Sonneratioideae still represent the monotelic type, whereas in the majority of the genera polytelic inflorescences are found. These often show a botrytic ramification, although the basic type of ramification is a thyrse. Among the great diversity of forms the gradual specialization of a short shoot-long shoot system can be observed, especially in the genus Ginorea. The same can be seen within the Combretaceae, which are polytelic throughout. As in most Myrtales families, phylloscopic buds or branches are frequently occurring and sometimes form a determinating factor for the shape of a flowering plant. In Onagraceae polytelic structure of inflorescences is also manifested throughout the family and florescences as botrya or spikes are known. On this basis an impressive diversity exists, especially in the variations of the proportions between the terminal main florescence and the extension of the enrichment zone, the number and size of paracladia, the length of the internodes, and the possibility of a reversion of the inflorescence apex to vegetative growth, commonly called proliferation. The latter often occurs in the inflorescences of Myrtaceae in which the "central type" and perhaps the phylogenetically primitive form is a monotelic thyrsoid or a panicle. Even in proliferating or in truncate synflorescences the monotelic character is evident by the fact that all paracladia, including those with more than one pair of flower-bearing branches, are provided with a terminal flower. The effloration of the proliferating inflorescence can be delayed for such a long time that the proliferating shoot may even form branches above the flower-bearing zone. Thus inflorescences of this shape sometimes were regarded as "intercalary inflorescences." In some cases (some species of Eugenia) the transition to the polytelic type seems to be compolete. In the majority of the Penaeaceae the inflorescences forming thyrsoids or stachyoids follow the monotelic type. Some facultatively or constantly truncate synflorescences form a transition to taxa with polytelic synflorescences. In Psiloxylaceae the flower-bearing systems are brachyblasts reduced to their botrytic florescence and inserted on older axes. Variety of inflorescences in Melastomataceae corresponds to the size of the family but shows less diversity than Myrtaceae. The inflorescences are monotelic. Cases of complete transitions to polytelic structures were not found. Even truncation seems to be rare and only a single case is reported for Medinilla magnifica. On the other hand, proliferation is not rare.