nd the
ginger-plants (_Zingiberaceae_), tropical herbs, generally of great
beauty.

The underground parts of certain tropical plants (_Dioscoreaceae_) are
known as "yams." A representative of this order exists in England in the
climbing black bryony (_Tamus_) of our hedges, and to the same group
belongs the very singularly stemmed elephant's foot, or tortoise-tree
(_Testudinaria elephantipes_). The last-named plant is a native of the
Cape of Good Hope, where it has been known as Hottentot's bread, because
the soft interior of its swollen base was at one time eaten by the
natives of that region, who have, however, now abandoned it to the
baboons.

Lastly, in this connexion may be mentioned the very interesting and
beautiful group of orchids (_Orchidaceae_), many of which live high up
in the air, supported on the branches of trees, from which their roots
hang freely down. Such orchids are sometimes spoken of as "air-plants."

All the Angiosperms as yet mentioned, from the grasses to the orchids
inclusively, belong to the lower of the two great groups or classes into
which, as was lately said, the whole mass of Angiosperms is divided.

This great group is named _Monocotyledones_ (on account of the structure
of the seed), and it is sometimes spoken of as _Endogens_, in reference
to a generally prevalent habit of growth. The members of this whole
class will then hereinafter be spoken of as "Monocotyledons."

All the plants which yet remain to be enumerated belong to the other and
still greater group of Angiosperms called (also in reference to their
seeds) _Dicotyledons_, a group sometimes spoken of as "_Exogens_," in
reference to the habit of growth prevalent amongst its species.

All our familiar trees which are not conifers, and most of our flowering
shrubs and herbs, are "Dicotyledons."

Amongst the many orders which compose the Dicotyledonous group the few
following may be selected for enumeration, either on account of the
general interest they possess, or because they will have to be more or
less referred to hereafter.

We may thus note the singular order of vegetable parasites, the
_Loranthaceae_, an order containing some thirty genera with four hundred
species, and including the mistletoe, which is traditionally venerable
in our island. The great group of catkin-bearing trees (_Amentaceae_),
contains a great assemblage of plants, familiar in England, such as the
hornbeam, hazel, oak, beech, Spanish chestnut,