viii
All these variations are available for the purposes of classification and doubtless
when thoroughly investigated, with special reference to this object, will furnish
very sufficient secondary circles. The zoned angiosperms Zonagens may then
perhaps be found to represent the Typical circle, the parallel or analogy of Mam-
malia; the Homogens the sub-typical, the parallel of Birds; while the Gymno-
gens, the Rhyzanths (Hysterogens) and Podostemons (Protogens) would unite to
form the aberrant circle. In this case the first would represent in the Exogenous
circle, and have for its analogies in the general system of plants, the Dicotyledons
the 2d the Monocotyledons, the 3d the Acrobrya or ferns, the 4th Hysterophyta
or Fungi, and the last the Protophyta or sea weeds. Here we have a series of
apparently circular groups all based on anatomical structure and physiological
peculiarities, without reference to the anatomy of the seed, except in so far as re-
gards the embryo. Whether these when properly analysed will prove perfect
circles is a point still to be ascertained. It is a difficult enquiry and the whole
subject is far too deeply involved in obscurity for me to offer any opinion in anti-
cipation, beyond the passing remark that these groups have a circular appearance
and give promise that, though they may not supply all we want, yet that their
thorough investigation may put us on the right path and speedily enable us to
reach the long and anxiously sought for goal.
Endogens have a stem increasing in thickness by additions of new matter to the centre, made up of vascular and cellular tissue, without distinction of pith, wood, medullary rays, or bark: the cellular tissue being traversed by bundles of vessels, often, as in all the arboreous forms, Palms, the surface first becoming hard and woody or as it were crustaccous. Leaves with parallel veius connected by smaller transverse ones, usually sheathing at the base and not readily separat- ing by articulation. Flowers usually ternary, with both calyx and corolla, but Sometimes both series so closely resembling each other in colour, size, texture, and form as to be undistinguishable; or occasionally they are imperfect or alto- gether wanting. Seed in a pericarp. Embryo furnished with albumen or rarely exalbumenous, with one Cotyledon, or if more, alternate, (not opposite as in dico- tyledons) the radicle enclosed within the Embryo through which it bursts in ger- mination.
From this general description it would appear there is a uniformity of struc- ture of both the vegetation and seed, little favourable to the formation of well defined groups. This however on closer inspection is not found to be the case as regards the habit and vegetation of several tribes. We have for example the Lilaceous class, as understood by Redoute, including nearly all the gay flow- ering herbaceous forms. The palms. The Retose families of Lindley, represent- ing the Homogens, generally composed of climbing shrubs with homogenous wood and dicotyledonous foliage but monocotyledonous seed. The Aroideous families,
