336 Structural and Physiological Botany, — 
III. NUDIFLORA. _ IV. GLUMALES. 
Pandanez. Eriocaulez. 
Aroidez. ~~. Centrolepidese. 
Typhaceze. Restiaceze. 
Lemnaceze. Cyperaceze. 
Naiades (including Juncaginez). Graminez. 
Alismaceze (?). ED. ] 
Cuass XIV. Daucotyledones. 
Dicotyledons are distinguished from Monocotyledons 
by the embryo having two cotyledons, by the structure of 
the stem, and by the prevalent number of parts in the floral 
whorls being [4 or] 5. 
The stem.consists, as a rule, of four parts, aronee dif- 
ferentiated from one another,—Epidermis, Cortex, Fibro- 
vascular Bundles, and Fundamental Tissue. 
A well-developed epidermis provided with stomata and 
often with subsidiary organs, entirely covers the younger 
parts. Earlier or later, often even in the first year, it 1s 
thrown off by the formation beneath it of a corky tissue, that 
part of the plant then losing its green colour. 
The cortical tissue is very commonly separated into two 
portions, an outer and an inner cortex. At an early period 
in its development bast-fibres, bast-vessels, and laticiferous 
vessels are generally distributed through it, in addition to 
the parenchymatous tissue which is always present; the 
vessels containing, according to circumstances, chlorophyll, 
' starch, crystals, tannin, latex, oil, resin, &c. In the course 
of its growth the cortex undergoes peculiar changes, with 
which we are not yet thoroughly acquainted, especially 
in the case of perennial plants. It is at first greatly 
stretched from within by the tissue formed beneath it, and 
finally split. The crevices and wounds thus formed are ; : 
partly filled up by the new cells of the bast-portion of the . | 
vascular bundles and those of the intermediate tissue, Part 
