Abstract

An inflorescence is a cluster of flowers in which the branches and leaves have been more or less modified. Most Dicotyledons have either a determinate or an indeterminate inflorescence. But there is another type of inflorescence having an indeterminate arrangement of flower-branches on the main axis and a determinate arrangement of flowers on the branchlets or branches and thus they may be called a 'mixed inflorescence'. Some mixed inflorescences, whose appearance is paniculate, are designated 'thyrses' or 'thyrsis'. The definition of a 'thyrse' in Bailey's Manual is a 'compact and more or less compound panicle; more correctly a pani-clelike cluster with main axis indeterminate and other parts determinate'(1). Youngken(16) has also defined a thyrse. He said: 'A thyrse is a mixed infiorescence more or less pyramidal or oblong in shape, consisting of a panicle of cymes'. In other words, the thyrse must meet at least two conditions: (1) it is composed of many determinate, triflowered cymes; and (2) these cymes or the branches of cymes are indeterminately arranged on the main axis.