It is often assumed that monocotyledons are descended from some lower group of dicotyledons, probably allied to that which includes the buttercup family.
We should then have to regard the Monocotyledons as a side-line, diverging probably at a very early stage from the main dicotyledonous stock, a view which many botanists have maintained, of late, on other grounds.
So far, however, as the palaeontological record shows, the Monocotyledons were little if at all later in their appearance than the Dicotyledons, though always subordinate in numbers.
On this view the monocotyledons must be assumed to have lost the cambium and all its influence on secondary growth, the differentiation of the flower into calyx and corolla, the second cotyledon or seed-leaf and several other characters.
It must be admitted that the whole question of the evolution of Monocotyledonsremains to be solved.
All these points are common to Monocotyledons and Dicotyledons, and separate the Angiosperms collectively from all other plants.
The last order of the monocotyledons is composed of marsh or water plants, some of which recall certain of the dicotyledons.
The leaves of the aroids are generally large and sometimes compound, the only instance of true compound leaves among the monocotyledons (Fig.
According to Eichler's classification, the monocotyledonsmay be divided into seven groups; viz.
The monocotyledons comprise many familiar plants, both ornamental and useful.
These are the fibro-vascular bundles which in the monocotyledons are of a simple type.
The abundance of Angiospermous dicotyledons, that of the monocotyledons of diverse families, but especially the Palms, during a part at least of this period, immediately distinguish it from the most ancient periods.
It cannot be doubted that the conditions favourable to the preservation of Monocotyledonsand Equisetums would have secured the preservation of some of the Apetalae, had they existed.
On account of their higher organization, they are easily distinguished from both Monocotyledons and Gymnosperms; and they present features which clearly differentiate them amongst themselves.
Your attention has been directed to the monocotyledons as an example, where retrogression is everywhere so active that it can almost be said to be the prevailing movement.
Sometimes it prevails, and the monocotyledons are obviously a reduced branch of the primitive dicotyledons.
The whole evolution of the monocotyledons from the lowest orders of dicotyledons implies the seeming loss of cambial growth and many other qualities.
The best point of his system is that, by reason of their characteristic differences of leaf structure, he distinguishes the classes now known to us as Monocotyledons and Dicotyledons.
The origin of the Monocotyledons and Dicotyledons remains one of the most difficult and attractive problems of Palaeobotany.
The conditions do not seem very different from the Tuff Galapagos Island, but, as far as I remember, very few monocotyledons there.
But why, oh, why should so many monocotyledons have come there?
Most Dicotyledons need 3–5 months, while Monocotyledons retain traces of poison for six months after its absorption.
Monocotyledons have no layer which has the power of producing new wood, and their growth takes place entirely from the intercalation of new bundles, which originate at the bases of the leaves.
They have already distinguished parallel-veined from netted-veined leaves, and learned that this difference is a secondary distinction between monocotyledons and dicotyledons.
The parallel-veined leaves of monocotyledons have stems without distinction of wood, bark and pith; the netted-veined leaves of dicotyledons have exogenous stems.
What a strange union of roots, that of monocotyledons in the main divisions, and of pure acrogens in the minor!
This was, however, retained for the specimens belonging to the Monocotyledons and Cryptogams, while those of the Dicotyledons were arranged in the new and spacious building of No.
Of these also there existed at first only the lower groups without distinct corollas, the Monocotyledons and the Apetalae.
Each whorl of its flower contains in most cases three leaves, and it is very probable that the mother plants of all Monocotyledons possessed a regular triple blossom.
The orders are carefully characterized, and those of Angiosperms are grouped in fourteen classes under the two main divisions Monocotyledons and Dicotyledons.
This, however, does not entitle us to assume the origin of Monocotyledons from Dicotyledons, although there is manifestly a temptation to connect helobic forms of the former with ranal ones of the latter.
Exalbuminous Monocotyledonsare either hydrophytes or strongly hygrophilous plants and have often peculiar features in germination.
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.
In Monocotyledons a similar advance from hypogyny to epigyny is observed, and from the dorsiventral to the radial type of flower.
The same effect of separation in working out diversity in structure is shown by the Monocotyledons as was shown by the eastern and western Cycads, and the northern and southern Conifers.
One of the facts in connection with the distribution of Monocotyledons is quite puzzling, and that is the very poor representation of the whole group in the southern hemisphere.
Some prominent facts in reference to the geographical distribution of these Monocotyledons are as follows: They contain four great families, which include almost one-half of their number, and which have become world-wide in their distribution.
Another fact in reference to theMonocotyledons is that they include an unusual number of families which are entirely aquatic in their habit.
A third fact of importance is that the Monocotyledons are mainly massed in the tropics, and in this sense are almost an exact contrast to the Conifers we have been considering above.
The whole of Monocotyledons appear to me (from anatomical reasons especially) to be degradations from Dicotyledons, and primarily through the agency of growth in water.
So, the ferns, lycopods, conifers, and monocotyledons of the palaeozoic and mesozoic rocks, have developed into the marvellous wealth of forms of the higher dicotyledons that now adorn the earth.
We now come to the true flowering plants, and we first meet with monocotyledons in the Carboniferous and Permian formations.
Amongst monocotyledons an analogous change occurs not unfrequently, as in some commelynaceous plants, e.
Among monocotyledons Convallaria majalis may be mentioned as very liable to suffer diminution in the number of its carpels, either separately or in association with other changes.
Among monocotyledons this partial development seems to be even more frequent than in dicotyledons.
The highest apetalous plants contain camphors and oils; the highest of the monocotyledons contain a mucilage and oils; and the highest dicotyledons contain oils and special acids.
With a few exceptions, and nature seems to delight in producing a few such, all monocotyledons have this parallel-veined leaf character and flower parts in threes or multiples of three.
Includes all the remaining flowering plants and is a larger group than the monocotyledons and the cone-bearing plants combined (Figures 78-81).
Thus the monocotyledons begin with the cat-tails, which have mere bristles for calyx and corolla, and lead by infinite gradations to the showy and highly complex orchids, which are considered the climax of the monocotyledonous families.
Many botanists believe that all the monocotyledons should be placed after the dicotyledons, as the latter may be a more ancient type than the former.
Recent work has thrown no decisive light on the question, but it has undoubtedly demolished the old view which supposed that the Monocotyledons (the lily group) appeared at a far earlier date upon this earth than the Dicotyledons.
Recent work, which has carefully sifted the fossil evidence, can only say that no true Monocotyledons have yet been found below the Lower Cretaceous rocks, and that at that period we see also the sudden inrush of Dicotyledons.
Monocotyledons and Dicotyledons existed in the Upper Cretaceous times.
The leaves are those of both Monocotyledons and Dicotyledons, and the genera are usually directly comparable with those now living, and sometimes so similar that they appear to belong to the same genus.
In the dicotyledons root and shoot are represented as springing from the same point, and in monocotyledons from opposite poles in the seed.
The distinction between dicotyledons and monocotyledons is accurately set forth, though the stress is laid not so much on the cotyledonous character of the seed as on the relation of root and shoot.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "monocotyledons" in a variety of sentences. We hope that you will now be able to make sentences using this word.
