1518 



CORMOPHYTA. 



Fig. 1385. — Circinate terminations of 

 young branches of Psilophyton prin- 

 ceps. (After Dawson.) 



regarded by Sir J. W. Dawson as forming a connecting link between 

 the Rhizocarps and the Lycopods, and probably forms the type of 



a distinct family, the Psilophytece. 

 This genus, with which Haliserites is 

 identical, occurs in the Lower De- 

 vonian of both Europe and the 

 United States, and is a plant of 

 more than average interest. It at- 

 tains considerable dimensions, and 

 has minute or rudimental leaves, 

 which are numerous and spirally 

 arranged on the barren stems, but 

 are sparse or absent on the fertile 

 ones. On decorticated stems their 

 point of attachment is represented by minute scars. The young 

 branches have circinate terminations (fig. 1385), like the "crosiers" 

 of Ferns ; while the rhizomes are circular, and show irregularly placed 

 areolae, to which the roots were attached. 

 The inner structure of the stem consists of 

 an axis of scalariform tissue, surrounded by 

 cells. Finally, the fructification (fig. 1386) 

 consists of naked oval sporangia, generally 

 borne in pairs on lateral or terminal pedi- 

 cels, which are regarded by Sir J. W. 

 Dawson as making the nearest approach to 

 the sporocarps of the Rhizocarps. Arthro- 

 stigma, from the Devonian of Canada, is 

 placed by the same authority in this family. 

 The three existing families of the order — 

 viz., Lycopodiece, Psilotecz, and Phylloglossece 

 — are of but little palaeontological import- 

 ance • the last two being unknown in a 

 fossil condition. Lycopodium occurs in the 

 Jurassic ; while in the Permian, Carbon- 

 iferous, and Upper Devonian there occur 

 allied forms for which the name Lycopo- 

 dites has been proposed. The Devonian 

 L. Milleri is, however, a Psilophyton. 

 Lycopodites also occurs in Lower Mesozoic 

 beds in New Zealand. 



Order 2. Heterospore^e (Ligulatte). 

 — This order, now represented by Selagi- 

 nella and Isoetes, is distinguished by developing two kinds of spores 

 — viz., macrospores and microspores — and by the presence of ligulae 

 to the leaves. In both the prothallium is developed within the 



^TtTl 



Fig. 1386.— Reduced restora- 

 tion of Psilophyton princeps ; 

 from the Lower Devonian of 

 Canada. (After Dawson.) 



