Differentiating features of studied Tamarix in Mongolia

Taxonomically, Tamarix is one of the most difficult genera among the Angiosperms (Baum 1978). Some reasons are that Tamarix species show few distinctive external features, dissections of the tiny flowers are often indispensable, and the androecium provides the most important distinguishing features but the interpretation needs some experience.

The character of the inflorescence (whether they are terminal/aestival or lateral/vernal) is of no diagnostic value. Unfortunately, it is used as a principal key feature until recently. In addition, the specification concerning length and proportions of racemes and flowers of most Tamarix species are varying in relevant literature. Therefore serious identification is hard if not impossible. In this account only flowering material was determined using the monograph of Baum (1978).

For Central-Asia, a monographic treatment of the genus is necessary to clear the number of species within the Mongolian territory. In this account only three species are differentiated. Moreover, the important features after Baum 1978 are tabulated.

Features of studied Tamarix
species according to Baum (1978); FC: according Flora of China

Tamarix	leaves mm	racemes cm x mm	bracts	flowers	petals mm	disk’s/ filaments
T. arceuthoides	1-2.5	1.5-5 x 3-4	as long as pedicels, pedicels < calyx	5 merous, FC: completely open, caducouse	1-1.5	thin, between disk lobes
T. leptostachya	2-3 clasping	7-15 x 3 dense	longer than pedicels, pedicels = calyx, in lower part denticulate	5 merous, FC: deciduous	1.5	broadened, at apex of disk lobes
T. ramosissima	1.5-3.5	1.5-7 x 3-4	longer than pedicels, pedicels < calyx, in lower part denticulate	5 merous, persistent	1-1.75	thin, between emarginated disk lobes
T. elongata	1.5-3	6-9(13) x 7-8	longer than pedicels, pedicels =/> calyx, in lower part denticulate, narrowly triangular	4 merous, caducouse	2.5-3	broadened, rising at apex of disk lobes

data compiled by: S. Rilke