. Ein Handbuch der cryptogamic Botanik. Kryptogamen. Fossile VASKULÄRE KRYPTOGAMEN li § Radiolarie Rhizopod, Mai massulae von Azolla. Sir W. Dawson (Bull. Chicago Acad. Sc, 1886, S. 105) bezieht sich Organe der Fruktifikation ü-wörtlich aus dem Devon (=Erian) in Kanada und den nördlichen USA - und zuvor beschrieben, unter dem Namen Sporangites (daws), als sporangien von Lycopodiacese - zu einer Gattung fast Allied zu Salvinia, die er als Protosalvinia; aber, insofern sie auf Lepidoden - dron Waage getragen, diese Erklärung ist unzulässig. Sir W. Dawson glaubt der Megaspores von Rhizocarpese

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. A handbook of cryptogamic botany. Cryptogams. FOSSIL VASCULAR CRYPTOGAMS li§ Radiolarian Rhizopod, may be massulae of Azolla. Sir W. Dawson (Bull. Chicago Acad. Sc, 1886, p. 105) refers organs of fructification ob- tained from the Devonian (=Erian) in Canada and the northern United States—and previously described, under the name Sporangites (Daws.), as sporangia of Lycopodiacese—to a genus nearly allied to Salvinia, which he calls Protosalvinia ; but, inasmuch as they are borne on Lepidoden- dron scales, this explanation is inadmissible. Sir W. Dawson believes the megaspores of Rhizocarpese to be the chief cause of the highly bituminous character of the shales in which these bodies are found. Fossil Selaginellace^. Remains of arborescent vegetation more or less nearly allied to the typical Selaginellaceae of the present day occur in extraordinary abun- dance in the older fossiliferous strata. Of these the most abundant and best known families are the Lepidodendrese and the Sigillariese. Of the LepidodendrE/E the stems are known as Lepidodendron, and the fructification occasionally found in organic connection with the. Fig. 87.—A, B, C, portions of surface of stem of diflferent species oi Lepidodendron (natural size) ; D, single cushion (magnified). (After Solms-Laubach.) branches, as Lefidostrobus. The fructification is distinctly heterosporous ; and although, in a large number of Lepidostrobus cones, microspores only have been detected, this is unquestionably either because the portion con- taining the megaspores has not been preserved, or possibly because the megasporanges and microsporanges may have been distributed in distinct fructifications—a degree of differentiation unknown in any existing form. The remains of a large number of species of Lepidodendron occur in the coal measures. They were trees, with stems up to ninety feet in height and two feet in diameter, covered with the diamond-shaped scars of fallen leaves. These scars, together with a por

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• bookcentury1800
• bookdecade1880