is an attempt to arrange as far as possible in a linear series those
orders which are characterized by absence or freedom of petals. The
second subclass, Gamopetalae, includes 9 series and culminates
in those which show the most elaborate type of flower, the series
Aggregatae, the chief representative of which is the great and
wide-spread order Compositae. A modification of Eichler's system,
embracing the most recent views of the affinities of the orders of
Angiosperms, has been put forward by Dr. Adolf Engler of Berlin, who
adopts the suggestive names Archichlamydeae and Metachlamydeae for the
two subdivisions of Dicotyledons. Dr. Engler is the principal editor
of a large series of volumes which, under the title _Die naturlichen
Pflanzenfamilien_, is a systematic account of all the known genera
of plants and represents the work of many botanists. More recently
in _Das Pflanzenreich_ the same author organized a series of complete
monographs of the families of seed-plants.

As an attempt at a phylogenetic arrangement, Engler's system is now
preferred by many botanists. More recently a startling novelty in the
way of system has been produced by van Tieghem, as follows:

Monocotyledons.
Liorhizal Dicotyledons.
Dicotyledons.
INSEMINEAE.
SEMINEAE.
_Unitegmineae.
Bitegmineae_.

The most remarkable feature here is the class of Liorhizal
Dicotyledons, which includes only the families of Nymphaeaceae