A, _Odontopteris subcuneata_ (Bunbury). B, _Neuropteris cordata_ (Brongniart). C, _Alethopteris tonchitica_ (Brongniart).] Beginning with the Mares’-tails, we find these represented in the Carboniferous by many gigantic species, attaining to almost tree-like dimensions (Fig. 96). These are the _Calamites_, which formed dense brakes and jungles on the margins of the great swampy flats of this period. Their tall stems, ribbed and jointed, bore whorls of leaves or branchlets. Sending out horizontal root-stocks and budding out from the base, they grew in great clumps, and had the capacity to resist the effects of accumulating sediment by constantly sending out new stems at higher and higher levels. The larger species assumed a complexity in the structure of their stems unknown in their modern congeners, and enabling them to grow to a great height;[31] but their foliage and fructification were not correspondingly advanced. Thus the family of the Equisetaceæ culminated in the Carboniferous, and thenceforth descended gradually in the succeeding ages, leaving the comparatively humble Mares’-tails and Scouring Rushes as its present representatives. The Ferns of the Carboniferous, like those of the Devonian, presented both gigantic forms like those of the tree-ferns of the modern tropics, and delicate herbaceous species, and these in great profusion. On the whole, they do not strike the observer as very dissimilar from those of modern times. A more critical examination, however, shows that the bulk of the tree-ferns of the Devonian and Carboniferous are allied not to the Polypod type, which is the most common at present, but to certain comparatively rare southern ferns, the _Marattias_ and their allies, characterised by a peculiar style of fructification, perhaps adapting them to a moist and warm atmosphere (Fig. 97).[32] Thus the ferns, while a wonderfully persistent type, were in their grander forms far more widely distributed in the Carboniferous than at present; and genera now comparatively rare, and limited to warm and moist climates, were then abundant, and ranged over those temperate and boreal regions of the Northern Hemisphere where only a few humble and hardy species can now subsist. There were also some remarkable and anomalous tree-ferns, of which that represented in Fig. 98 is an example. [Illustration: FIG. 98.—Carboniferous Tree-ferns. A, _Megaphyton magnificum_ (Dn.). C, _Palæopteris Hartii_ (Dn.). D, _P. Acadica_ (Dn.).]