﻿382 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



resembles a fern in the habit of its delicate quadripinnate frond, the 

 anatomy of its leaf, and its primary wood, while by the structure of 

 the leaf trace bundles and secondary wood, with pitted tracheides, 

 it appears to be related to the Cycadales. 



The average Heterangium stem is less than 1.5 cm. in diameter, 

 and includes : ( 1 ) a large central primary cylinder of anastomosing 

 primary wood strands mingled with conjunctive parenchyma very 

 much as in Medullosa, the outer wood strands, of mesarch col- 

 lateral structure, with spiral, reticulate and pitted (multi-seriate, 

 bordered) tracheides, forming a row, from which the leaf traces 

 originate; (2) a thin zone of secondary wood, with tracheides 

 bordered-pitted on the radial walls, and with broad medullary rays 

 which give it a loose spongy texture; (3) a cambium; (4) phloem; 

 (5) pericycle; (6) an inner cortex of short-celled parenchyma con- 

 taining vertical rows of transverse sclerotic plates, comparable to the 

 stone cells of living plants; (7) an outer cortex containing vertical 

 strands forming radial and distantly anastomosing hypodermal plates. 

 Adventitious roots spring from the primary wood strands. The 

 petiolar strands, which, in one species, contain traces of secondary 

 wood, are at first collateral, but become concentric on entering the 

 petiole, which contains a single strand. The delicate frond is abso- 

 lutely filicoid, tripinnate, and finely cuneately dissected, that of 

 Heterangium Grievii being indistinguishable from, if not identical 

 with, Sphenopteris elegans. 1 



The fructification of Heterangium is not definitely known, but it 

 is possible that the male sporangia belong to the type described by 

 Stur 2 as Calymmatotheca. The structures of primary stem, thick 

 pericycle, and of petiole also are fern-like and have been compared 

 by Doctor Scott with Gleichenia; but the mesarch outer primary 

 strands, and the characters of the secondary wood, with pitted 

 tracheides, strongly suggest the stems and petioles of Cycads. 



Lyginopteris. — Very closely related to Heterangium is the genus 

 Lyginopteris of Potonie 3 (Lyginodendron Williamson), for whose 

 beautiful and complete elaboration we are indebted to Williamson 4 

 and Scott. 5 In the form of its fronds, its microsporangia, and in 



1 Phil. Trans., vol. 163, 1873, P- 377; vol. 164, pt. 2, 1S74, P- 675; vol. 166, 

 1876, p. 1; vol. 178B, 1887, p. 289; vol. i8ib, 1890, p. 89. 



2 Phil. Trans., vol. i86b, 1896, p. 703. 



8 Lehrb. d. Pfianzenpalmont., p. 171. 



* See Slur, Abh. d. k.-k. gcol. Rcichsanst., vol. vnr, pt. 2, Wien, 1877, p. 

 130. 



5 Loc. cit, p. 149. See also Kidston. Trans. Roy. Soc. Edinb., vol. xxxit, 

 pt. 1, 1889, p. 137. 



