1514 



CORMOPHYTA. 



Fig. 1379- — A leaf- whorl 

 of Prota.7inula.ria Harknessi ; 

 from the Ordovician of the 

 North of England. 



habits, the linear pinnae of the leaves acting as floats. Finally, 

 there remains for consideration the imperfectly-known plants from 

 the Ordovician (Arenig beds) of England to which the hybrid name 

 Protannularia has been given ; and which were originally referred 

 to the Thallophytous genus Buthotrephis. 

 They consist of slender branching stems 

 bearing at intervals whorls of linear leaves 

 (fig. 1379), somewhat resembling those of 

 the Equisetaceae, to which class they may 

 be more or less closely allied. 



Class II. Equisetace^e. — With this 

 group we come to a small class now repre- 

 sented by only a single genus with species 

 of comparatively small size, but which in 

 the Palaeozoic contained numerous forms of 

 large dimensions, and occupying an import- 

 ant position in the contemporary vegetation. 

 The class may be briefly characterised by 

 the rudimentary condition of the leaves, 

 which are reduced to small sheathing whorls, borne either on the 

 stem or on branchlets also arising in whorls from the joints of 

 the barren stem. The sporangia, which produce only one kind of 

 spores, are borne upon specially modified leaves forming a terminal 

 spike to the main stem (fig. 1381, a), there 

 being distinct fertile and barren stems. 



The existing family Equisetece comprises 

 small forms, characterised by their perennial 

 rhizome, from which the annual stems arise. 

 The single existing genus Equisetum (Horse- 

 tails) occurs in most parts of the world, with 

 the exception of Australasia ; and seems to 

 have commenced in the Lower Keuper, where 

 species of much larger size than their existing 

 analogues are met with ; and from this period 

 representatives occur throughout most of the 

 European Mesozoic and Tertiary strata and 

 also in some of those of North America, and 

 in the Lower Mesozoic of New Zealand. The 

 Carboniferous Equisetites seems to have been 

 an allied genus. 



The extinct family Schizoneurea is typically 

 represented by the genus Schizoneura (fig. 

 1380), which occurs throughout the European Trias, and perhaps 

 also in the Jurassic, and in the Lower Gondwanas of India. Ac- 

 cording to Dr Feistmantel, these plants are characterised by the 



Fig. 1380. — Schizoneiira 

 gondwanensis ', from the 

 Damuda series of India. 

 Much reduced. (After Feist- 

 mantel.) 



