148 PSARONIUS. 



anastomose from time to time, and sometimes the entire vascular 

 cylinder is surrounded by a closed sclerenchymatous band. Steles 

 concentric, with a central strand of scalariform tracbeides, sur- 

 rounded by phloem. The leaf-traces arise from the peripheral 

 steles of the cylinder, and have the form of bands concave 

 towards the centre of the stem. The adventitious roots have 

 a central axis consisting of a polyarch stele, formed of a variable 

 number of radiating woody strands, with a similar number of 

 phloem strands between them. Inner cortex of the root 

 parenchymatous, sometimes solid, sometimes lacunal ; outer cortex 

 sclerenchymatous. 



The Psaronii form a numerous group, which has been sub- 

 divided by Zeiller into three divisions, based on the phyllotaxis. 

 These are the Pulystichi with numerous vertical rows of leaves, the 

 Tefrastichi with four rows, and the Distichi with two rows. The 

 species described here belongs to the Tefrastichi. 



Several species of Psaronim are known to have been the stems 

 of plants possessing the Pecopteris type of foliage, especially the 

 Pecopterids bearing the fructifications known as Scolecopteris and 

 Asterotheea. Such plants present a close resemblance to a modern 

 family of ferns, the Marattiacese. 



Distribution. — Pernio- Carboniferous (Northern Type) : — In the 

 Upper Carboniferous and Permian of Europe, especially the latter. 

 Pernio- Carboniferous (Glossopteris Type): — Brazil. 



Psaronius brasiliensis, linger. 



(Plate VII.) 



1831-50. Psaronius brasiliensis, linger, in Martius' Hist, natur. Palmarum, i, 

 p. lxx, pi. geol. i, fig. 4. 

 1872. P. brasiliensis, Brongniart, Bull. Soc. hot. France, ser. v, vol. xix, p. 3. 



1889. P. brasiliensis, Bennett & Murray, Handb. Cryptog. Botany, p. 123, 



text-fig. 95. 



1890. P. brasiliensis, Zeiller, Bass, liouill. et perm. d'Autun et d'Epiuac, 



fasc. ii, pt. 1, p. 246, pi. xxi. fig. 1. 



1891. P. sp., Solms-Laubaoh, Fossil Botany, Eng. edit., p. 170. 



1895. P. brasiliensis, Zeiller, Bull. Soc. Geol. France, ser. in, vol. xxiii, 



p. G05. 

 1900. P. brasiliensis, Scott, Stud. Foss. Botany, p. 271, text-fig. 96. 

 1904. P. brasiliensis, Sohns-Laubach, Festschr. P. Ascherson's Sicbzigsten 



Geburtet., p. 18. 



