Taxonomic Studies On The Genus Crassula L.

Abstract

The difficulties involved in the taxonomy of the genus

Crassula, such as the extensive variation and often difficult

species complexes, vicariousness and hybridization, are sketched

against a historical background. These difficulties have prompted

the author to review concepts of taxa from subspecific to generic

level and have also le~ to the approach adopted in this work.

It is argued that in several genera and sections, as

previously recognized, too much stress was placed on the several

floral characters which form part of a pollination syndrome which

is shown up by convergent developments of these flower typeso

The diff~rent types of seedling mprphology recognized

are considered in relation to the morphology of adult plants and

their affinities at specific and sectional level.

The distribution of the hydathodes has proved useful in

the delimitation of supraspecific taxau ThB morphology of the

developing seedlings and the distribution of the hydathodes on ,

the leaves become the main arguments for a new classification in

the genus Crassula.

A cytological review stresses the different basic chromosome

numbers (8,7) and their structural differences for the de~

limitation of the subgenerao Problems in determining the original

basic number and the high percent~ge of polyploidy with various

rainfall conditions are evaluated.

Subsequently the characteristics and affinities of

Crassula and its subgeneric taxa are briefly discussed.

The key to the species, subspecies and varieties is

divided into twelve groups which are similar to sections or groups

of sections recognized.