De Candolle divides the class of exogensinto four sub-classes according to the arrangement of their flowers &c.
The Upper Cretaceous rocks, however, both in Europe and in North America, have yielded an abundant flora which resembles the existing vegetation of the globe in consisting mainly of Angiospermous Exogens and of Monocotyledons.
Up to the close of the Lower Cretaceous, no Angiospermous Exogens are certainly known to have existed, and Monocotyledonous plants or Endogens are very poorly represented.
The great majority of the Eocene plants are referable to the groups of the Angiospermous Exogens and the Monocotyledons; and the vegetation of the period, upon the whole, approximates closely to that now existing upon the earth.
Of the herbaceous exogens of the period we know less.
The structures of these remarkable trees, and the manner in which they anticipate those of the true exogens of modern times, have been admirably illustrated by Dr.
The flora is a warm temperate one, with some remarkable mixtures of sub-tropical forms, among which perhaps the most remarkable are Kaidocarpum referred to the Pandaneæ, and such exogens as Ficus and Cinnamomum.
The leaves of exogens have their veins in the form of a network, and the parts of the flower are generally arranged in whorls of two or five or of some multiple of these numbers.
A section of the rhizome exhibits the fibro-vascular tissue arranged differently from that in the stems of either Exogens or Endogens.
The annual rings of the Exogens are best observed in transversely sawn-off pieces of perfectly dry stems, which have been polished with sandpaper, and varnished with spirit varnish.
They are Gymnogens as to ovules, and neither Exogens nor Endogens in the wood of their short, simple, or branched trunks, and they have dicotyledonous seeds.
The entire absence, so far as our paleontological investigations have hitherto gone, of ordinary dicotyledons or exogens in the coal measures, is most remarkable.
Take the characters of exogens as distinct from endogens; even under ordinary circumstances, no absolute distinction can be drawn between them.
Exogens and Endogens are only the two kinds of flowering plants.
I should think the mushrooms might be Endogens from their stems, and the fern Exogens from their leaves.
I mean how many principal kinds--like flowers, you know--they areExogens and Endogens.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "exogens" in a variety of sentences. We hope that you will now be able to make sentences using this word.
