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Some represent natural groups and had in several cases been already recognized by Ray and others, but the majority are, in the light of modern knowledge, very mixed. Well-defined polypetalous and gamopetalous genera sometimes occur in the same order, and even Monocotyledons and Dicotyledons are classed together where they have some striking physiological character in common.
Do you know Jussieu divided all vegetables into three great orders Acotyledons, Monocotyledons, and Dicotyledons. It is only under the tropics that ferns attain the dimensions of the one you are looking at; in colder regions their height seldom exceeds a few feet.
The earth had been kept for three years, but when broken, watered and placed under a bell glass, no less than eighty-two plants sprung from it: these consisted of twelve monocotyledons, including the common oat, and at least one kind of grass, and of seventy dicotyledons, which consisted, judging from the young leaves, of at least three distinct species.
There are no annular rings. If possible, let the pupils compare the leaves belonging to these different types of stems. The parallel-veined leaves of monocotyledons have stems without distinction of wood, bark and pith; the netted-veined leaves of dicotyledons have exogenous stems. Dicotyledons have bark, wood, and pith, and grow by producing a new ring of wood outside the old.
The word endogenous, inside-growing, is not, therefore, a correct one to describe the growth of most monocotyledons, for the growth takes place where the leaves originate, near the exterior of the stem. Gray's First Lessons. Sect. VI. Sect, XVI, §1, 401-13. §3. §6, 465-74. How Plants Grow. Chap. 1, 82, 90-118.
When I visited Aix, I found the silicified wood of this plant very plentifully dispersed through the white sands in the pits near that city. In one silicified trunk 200 rings of annual growth could be counted. Species of Araucaria like those of Australia are also found. Cycads are extremely rare, and of Monocotyledons there are but few.
In albuminous Monocotyledons the cotyledon itself, probably in consequence of its terminal position, is commonly the agent by which the embryo is thrust out of the seed, and it may function solely as a feeder, its extremity developing as a sucker through which the endosperm is absorbed, or it may become the first green organ, the terminal sucker dropping off with the seed-coat when the endosperm is exhausted.
Only at a later period flowering plants appear, among them being first the plants with naked seeds standing lower in the systems, as the cycad-trees and pine-forests; later, those with enclosed seeds, among them being again first the monocotyledons, last the dicotyledons, all of them precisely corresponding to the botanical system. The same thing is true in the animal kingdom.
Humboldt and Bonpland found, among the unquestionably indigenous plants of tropical America, monocotyledons only, all the dicotyledons of those extensive regions having been probably introduced after the colonization of the New World by Spain. The seven hundred new species which have found their way to St.
We readily recognize in them now-a-days the natural classes of Dicotyledons and Monocotyledons distinguished alike in vegetative and in reproductive construction, yet showing remarkable parallel sequences in development; and we see that the Dicotyledons are the more advanced and show the greater capacity for further progressive evolution.
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