)
[Footnote 23: The "Flowering plants" are divided into the two
great groups of the Endogens and Exogens. The _Endogens_ (such
as Grasses, Palms, Lilies, &c.) have no true bark, nor rings of
growth, and the stem is said to be "endogenous;" the young plant
also possesses but a single seed-leaf or "cotyledon." Hence these
plants are often simply called "_Monocotyledons_." The _Exogens_,
on the other hand, have a true bark; and the stem increases by
annual additions to the outside, so that rings of growth are
produced. The young plant has two seed-leaves or "cotyledons,"
and these plants are therefore called "_Dicotyledons_." Amongst the
Exogens, the Pines (_Conifers_) and the Cycads have seeds which
are unprotected by a seed-vessel, and they are therefore called
"_Gymnosperms_." All the other Exogens, including the ordinary
trees, shrubs, and flowering plants, have the seeds enclosed in
a seed-vessel, and are therefore called "_Angiosperms_." The
derivation of these terms will be found in the Glossary at the
end of the volume.]
In North America, the Cretaceous strata of New Jersey, Alabama,
Nebraska, Kansas, &c., have yielded the remains of numerous plants,
many of which belong to existing genera. Amongst these may be
mentioned Tulip-trees (_Liriodendron_), Sassafras (fig. 186),
Oaks (_Quercus_), Beeches (_Fagus_), Plane-trees (_Platanus_),
Alders (_Alnus_), Dog-wood (_Cornus_), Willows (_Salix_), Poplars
(_Populus_), Cypresses (_Cupressus_), Bald Cypresses (_Taxodium_),
Magnolias, &c.
Pages:
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397