3iy 
Class III. ENDOGENS, or MONOCOTYLEDONS. 
Monocotyledones, Juss. Gen. 21. (1789); Desf. Mtm. Inst. 1. 478. (1796). — Endor- 
Rich. Anal. (1808). — Monocotyledones or Endogens, DC. Theorie, 
207. (1813). — Cryptocotyledones or Granifers, Agardh. Aph. 73. (1821). 
Essential Character. — Elementary organs consisting of both cellular and vascular 
tissue, a portion of the latter being elastic spiral vessels. Cuticle with stomates. Trunk 
usually cylindrical when a terminal bud only is developed, becoming conical and branched 
when several develope ; consisting of cellular tissue, among which the vascular tissue is 
mixed in bundles, without any distinction of bark, wood and pith, and destitute of medul- 
lary rays ; increasing in diameter by the addition of new matter to the centre. Leaves fre- 
quently sheathing at the base, and not readily separating from the stem by an articulation, 
mostly alternate, with parallel simple veins, connected by smaller transverse ones. Flowers 
usually having a ternary division ; the calyx and corolla either distinct, or undistinguisha- 
ble in colour and size, or absent. Embryo with but 1 cotyledon ; if with 2, then the acces- 
sory one is imperfect and alternate with the other ; radicle usually enclosed within the 
substance of the embryo, through which it bursts when germinating. 
Nothing can be more simple that the mode of distinguishing Monocotyle- 
donous from Dicotyledonous plants, notwithstanding the difficulty of fixing 
upon any single character of separation. It is true that the structure of the 
stem is not sufficient, because it is frequently impossible, in annual plants, to 
ascertain if it be Exogenous or Endogenous ; the parallel veins of the leaves 
of Monocotyledons do not always afford a constant character, because some 
genera have reticulated ones ; the want of articulation between the stem and 
the leaves, although very prevalent in Monocotyledons, sometimes changes to 
perfect articulation, as in Orchidaceae ; the ternary division of the fiower of 
Monocotyledons is often departed from, as in Aracese and the neighbouring 
orders ; many Dicotyledons have also ternary floral envelopes : Monocotyle- 
dons have sometimes more than one cotyledon, as the common Wheat ; finally, 
when the stem is capable of being strictly examined, a distinction between 
wood and pith occasionally exists, as in the common Rush ; and the conical 
branched character of Dicotyledons is assumed in Grasses and Asphodelese. 
Hence it is by a combination of characters that the two great divisions are 
to be known, and not by any absolute single mark : for instance, in Grasses, 
in which the stem is, as an eminent botanist has justly remarked, less 
Endogenous than in almost any other Monocotyledons, the leaves, flowers, 
and seeds, will shew them to be at once of the latter structure ; so in Juncus, 
in which pith is present, no other character is at variance with those of Mo- 
nocotyledons ; and again in Orchidaceae, in which a complete disarticulation 
of the stem and leaves takes place, every other point of structure is that of 
Monocotyledons. Brown has remarked (Cow^o. 481.), that the presence of 
albumen may be considered as the natural structure of this primary division ; 
seeds without albumen occurring only in certain genera of the paradoxical 
Aracese, and in some other Monocotyledonous orders which are chiefly 
aquatic. It is a fact well deserving attention, that Monocotyledons differ from 
Dicotyledons in their geographical distribution as well as in structure ; a seem- 
ing corroboration of the hypothesis, that the forms of vegetation are con- 
trolled by peculiarities of climate, acting in an unknown manner. From the 
enquiries of Humboldt, it appears that Monocotyledons form, in equinoctial 
regions, about l-6th of the flowering plants ; in the temperate zone, between 
36*^ and 52® latitude, l-4th; and towards the polar circle, nearly l-3d. 
