﻿WHITE] FOSSIL PLANTS 01 GROUP CYCADOFILICES 3 8 3 



the young roots Lyginopteris is typically a fern. In its stems, 

 petioles, and seeds it is largely Cycadaceous, though the stems pre- 

 sent some analogies with Osmunda also. 



The stems of Lyginopteris (see plate liii), which arc several cen- 

 timeters in diameter, 1 arc monostelic, the center being occupied by 

 a large pith, at the periphery of which occur several (5-8) large, 

 more or less isolated, collateral bundles of small spiral, scalariform, 

 and bordered-pitted tracheides in mesarch structure. Next we have 

 a thick zone of secondary wood consisting of radially and pluri- 

 seriately pitted tracheides and broad medullary rays, both direct and 

 secondary. The cambial zone is followed by phloem, which also is 

 rayed. External to this is the pericycle, several cells thick, a thin 

 periderm, a tender, inner, and a resistant outer cortex, which is 

 characterized by radial sclercnchymatous plates longitudinally flexu- 

 ose-anastomosing so as to form a rhomboidal net in tangential sec- 

 tion, the meshes being occupied by parenchyma (" Dictyoxylon 

 structure "). 



The leaf traces, arising from the chief primary strands, break 

 through the secondary wood, and are collateral and twinned while 

 ascending in the pericycle, but they become concentric and V- or 

 W-shaped, without secondary xylem, in the petiole. 



The adventitious roots, which were published as Kaloxylon by 

 Williamson prior to correlation with the stems, are described by 

 Doctor Scott as exhibiting in their early stages, less than 5 mm. in 

 diameter, 2-8 strands of primary wood in an arrangement closely 

 resembling that of the roots of the Marattiaceae, or of the Ophioglos- 

 saceae, though when larger they show secondary tissue in a structure 

 "absolutely indistinguishable from that of typical dicotyledons or 

 gymnosperms." 



The petioles (originally described as Rachiopteris aspera Will.) 

 of Lyginopteris oldhamia are found in organic union with the very 

 large, highly compound, finely dissected fronds of Sphcnoptcns 

 Hocningliausii Brongn., 2 one of the common species in the Lower 

 Coal Measures of Europe and America. These fronds are so typ- 

 ically filicoid that only anatomical identity in every detail or actual 

 union could suffice to remove them from their previously unques- 

 tioned place among the ferns. The reference of the Calymmato- 

 theca form of long, sack-like, clustered bodies, regarded as exannu- 

 late sporangia, to the Hocninghausii group of Sphenopterids has 



l L. robnstum Seward is represented as about 12 cm. in diameter. 

 2 Plate liii, Figure 2. See also Zeiller, Flore fossils du bassin houill. de 

 Valenciennes, 1888, p. 82, pi. V, f. 3. pi- vi, f. I, 2. 



