TRUNCI. 119 



plants in Engler and Prantl's Die naturliclien pflanzenfamilien.* 

 Saporta 2 and Renault 3 have also given some account of the 

 living cycads, and further details may be found in the writings 

 of Brongniart, 4 Miquel, 5 Richard, 6 Karsten, 7 Carruthers, 8 Solms- 

 Latibacb, and others. 



By far the greater number of known fossil stems have been 

 found in Lower Cretaceous and Jurassic strata, and it is with 

 these Mesozoic examples that we are at present concerned. In 

 Brongniart's Prodrome 9 there is recorded but one example of 

 a cycadean stem ; this is the plant described by Buckland from 

 the Portland dirt-bed, and for which the French author suggested 

 the name of Mantellia. The common Clathraria Lyelli, Mant., 

 is included by Brongniart among the Monocotyledons. In the 

 Tableau 10 we find several additions to the list of cycadean stems, 

 and among them is the interesting genus Medullosa of Cotta ; 

 this Palaeozoic plant has been subjected to a detailed investigation 

 by Gb'ppert and Stenzel, 11 Schenk, 12 and others, and we may 

 probably regard it as an extinct type of cycadean structure, 

 using the term cycadean in a wide sense. In 1828 Buckland 13 

 figured and described some large specimens of silicified stems 

 from the Isle of Portland, and, with the concurrence of Robert 

 Brown, instituted a new family, Cycadeoidece, for their reception. 

 Buckland fully recognized the close resemblance between these 

 "petrified birds' nests" and the stems of certain cycads; but 

 a new family name was proposed on account of some peculiarity 

 as regards the position and size of the rings of wood. In a 



1 Teil. ii. Abth. i. p. 6. 2 Pal. Fran9. vol. ii. 



3 (A. 4), Cours bot. foss. vol. i. p. 33. 



4 (2). 5 (1) and (3). 

 6 Richard. 7 Karsten. 



8 Carruthers (1). See also Solins-Laubach (3). 



9 p. 92. 10 p. 59. 



11 Goppert and Stenzel. In speaking of the Medullosece, Solms-Laubach 

 remarks (Fossil Botany, p. 100) that "that in their anatomical structure they 

 show many points of resemblance to the Cycadece, though they depart from them, 

 according to the most recent investigations, in some important particulars." 



12 Schenk. 13 Buckland (1). 



