452 



PALEOBOTANY. 



coal is actually made up of the sporangia of Lycopodiaceous plants. 

 The same thing is also occasionally seen in some shales, as, for example, 

 in the black shale of Kettle Point, on Lake Huron, the age of which is 

 Devonian. This shale is seen on inspection by the unassisted vision to 

 bo dotted all over with minute brown specks, which on a microscopic 

 examination of thin slices (fig. 704) are found to be the spherical spor- 

 angia of some of the Lycopodiacerc of the Devonian. The number of 

 these sporangia present in the shale is enough to render it combustible, 

 Avith some ditticulty : but it is not, of course, in any sense a true coal. 



As has l^een already observed, the types of plants which 

 are found in the Carboniferous rocks are to a great extent 



identical with those which com- 

 posed the Devonian flora. Speci- 

 fically, however, the coal-plants 

 are almost always distinct from 

 the DeA'onian forms. The num- 

 1)er of plants already known to 

 liave existed during the Car- 

 boniferous period is so great, 

 that nothing more can be done 

 here than to draw the attention 

 of the student to some of the 

 more important and character- 

 istic types. 



a. Filices. — The Ferns of the 

 Carboniferous period are ex- 

 tremely numerous, and include both herbaceous forms like 

 the majority of existing species, and arborescent forms simi- 

 lar to the living Xree- ferns of New Zealand. The latter 

 belong to the genera Fsnrormis} Caulopteris, and Fcdcvoptcris, 

 of which the two former occur in the older Devonian period. 

 Of the smaller ferns, the genera Sp1icno2oteris, Pecopteris, 

 Alcthopteris, Oclontoptcris, Ncuropteris, Hymenophyllitcs, and 

 Gycloptcris may be mentioned as the most important and 

 widely distributed. In the genus Ncuropteris (fig. 705) the 

 midrib of the leaflets is evanescent, either not distinct, or 

 disappearing towards the apex. Species of this genus are 



^ Psaronius appears to be the internal structure of the stems of Tree-ferns, 

 of which the genus Stcmmato2)tcris is the external aspect. 



Fig. 704. — A thin slice of shale from 

 Kettle Point, Lake Huron, showing 

 sporangia of Club-mosses, greatly mag- 

 nified. Devonian. (Original.) 



