318 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



Schizoneura, a type of the Permian and Triassic, had leaves which 

 were at first united in a sheath or in several broad sheath segments 

 that subsequently split into a varying number of multiple-veined 

 divisions. Neocalamites of the Triassic had free univeined leaves 

 greatly resembling those of Annularia in some of the late Triassic 

 species. Phyllotheca, a Permian and early Mesozoic type, had acic- 

 idar, slightly connate, univeined leaves and the sporangia were borne 

 by peltate sporangiophores alternating with whorls of sterile bracts. 

 Xematophvllum, Schizoneura, Neocalamites, and Phyllotheca are all 

 based upon impressions, so that a knowledge of the structure or the 

 details of organization of their fructifications is unfortunately 

 wanting. Structurally calamite leaves show a central trace sur- 

 rounded by a broad zone of mesophyll. 



Several generic types of calamites have been based upon stem 

 anatomy. These include Arthropitys (the Calamites vera of British 

 botanists) in which the pith was large and hollow except peripher- 

 ally, with persistent diaphragms at the nodes. Surrounding the 

 pith was a ring of collateral vascular bundles, the protoxylem in all 

 but the youngest stems being disorganized to form longitudinal pas- 

 sages known as carinal canals. The wood was entirely centrifugal 

 in its development. Secondary wood formation started early and 

 consisted of scalariform or radially pitted tracheids and variable 

 rays which continued with undiminished width through the vascular 

 cylinder or tapered outward or were abruptly shut off by interfas- 

 cicular wood. The cortex consisted of an inner thin-walled zone of 

 cells and an outer denser zone in which there was a very great de- 

 velopment of periderm. The courses of the leaf traces was some- 

 what varied and more complicated than in the Equisetales, otherwise 

 Arthropitys was much like an Equisetum with the addition of sec- 

 ondary thickening. A second type, known as Arthrodendron and 

 confined to the British Coal Measures, had a thin zone of wood, in 

 which the primary bundles were widely separated by the principal 

 rays which consisted of elongated fibrous elements (prosenchyma), 

 within which there were secondary rays of parenchyma like those of 

 the secondary wood. In the latter the tracheids are reticulate, and 

 the infranodal canals very large. A third type, Calamodendron, of 

 the European Upper Carboniferous and Permian, had radial bands 

 of prosenchyma containing secondary rays between the normal rays 

 and the radial bands of secondary wood. The roots of calamites pre- 

 served as impressions, which are of widespread occurrence, are 

 known as Pinnularia. Structural root material, known as Astro- 

 myelon, shows a usually persistent pith surrounded by a ring of 

 centripetally developed primary wood alternating with groups of 

 primary phloem. The zone of secondary wood was wide; the endo- 

 dermis appears to have been double; and the cortex was very thick 

 with large lacunar intercellular spaces, denoting a swampy or 

 aquatic habitat. 



