ho = 
Psaronius 
Cotta, Die Dendrolithen, 1832, p. 27. 
Under this name are included petrified trunks of tree ferns hav- 
ing a central wood cylinder surrounded by an usually thick cortical 
zone of parenchyma traversed by numerous descending adventitious 
roots. 
The woody cylinder contains a variable number of steles in 
the form of flat bands, often sinuate or hooked in section, arranged 
in concentric circles and anastomosing in a ground mass of pa- 
renchymatous conjunctive tissue. Anastomosing sclerenchymatous 
bands are, in some species, intercalated near the periphery, which 
is sometimes marked by a sclerenchymatous sheath. The individual 
stele is concentric in structure, consisting of a central strand of 
scalariform tracheides surrounded by phloem. 
The leaf strands, in the form of dorsally convex bands, spring 
from the anastomoses of the outer steles. Each intra cortical adven- 
titious root has a central polyarc stele distinctly stellate in section, 
an inner parenchymatous cortex, and an outer sclerenchymatous 
cortex. 
The fronds of Psaronius are included in Pecopteris and em- 
brace species with the Asterotheca and Scolecopteris types of fruc- 
tifications. They are most nearly related to the living Marattiaceae 
though representing a totally extinct tribe. In the Northern flora the 
genus occurs in the Stephanian and Permian of both Europe and 
North America. 
Psaronius brasiliensis Brong. 
4850. Psaronius brasiliensis Brongniart, mss., Unger 
in Martius, Hist. nat. palmarum, vol. 41, p. LXXX, pl. 
géol. 1, fig. 4; Brongniart, Bull. Soc. bot. Fr., (5) vol. 
XIX, 1872, p. 3; Bennett and Murray, Handb. Crypt. Bot., 
1889, p. 123, fig. 95 ; Zeiller, Fl. foss. bassin  houill. 
Antun et Epinac, pt. 1, 1890, p. 246, pl. XXI, fig. 15 Zeil- 
ler, Bull. Soc. géol Fr., (3) vol. XXIII, 1896, p. 605; 
Scott, Fossil Botany, 1900, p. 274, fig. 96; Solms-Laubach, 
