Phyllotaxis whorled

Phyllotaxy.—Phyllotaxy is the study of leaf arrangement upon the stem or branch, and this may be either alternate, opposite, whorled, or verticillate, or fascicled. It is a general law in the arrangement of leaves and of all other plant appendages that they are spirally disposed, or on a line which winds around the axis like the thread of a screw. The spiral line is formed by the union of... 

Ihe character for number of perianth whorls (Fig 4. IB) is not strictly applicable in flowers with spiral phyllotaxis, but we have treated the number of so-called series of... 

Based on our data set, there are no unequivocal changes in floral characters on the line from the base of the mesangiosperms to the common ancestor of Canellales and Piperales. If mesangiosperms originally had a trimerous androe-cium, as inferred when phyllotaxis and merism are treated as separate characters, there was an increase in the number of stamens per whorl in Canellales (i.e. the androecium became polymerous), followed by connation of the stamens into... 

Contrary to earlier beliefs, floral phyllotaxis patterns are very flexible. The direction is not only from spiral to whorled, but there was repeated evolution of spiral phyllotaxis from whorled in the perianth in basal angiosperms (Endress and Doyle, 2007, 2009 Doyle and Endress, 2011) and there is much evolutionary flexibility of patterns within families, genera or even species (Endress, 1987 Staedler and Endress, 2009). 

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