APPENDIX A 



615 



plants, though there are many exceptions. Three classes are recognized: 

 the ferns (Filicinae), the lower seed plants (Gymnospermae), and the 

 flowering plants (Angiospermae). In the older classification the ferns are 

 included in the division Pteridophyta along with the Lycopsida, and 



B 



1& 



Fig. A. 16. The Carboniferous lycopod Sigillaria, a massive tree which grew to be 100 feet 

 tall and 6 feet in diameter. It reproduced by spores, borne on cones up to a foot long and an 

 inch or two in diameter. The gametophyte generation produced from these spores is 

 unknown. A, the entire tree. B, a leaf. C, D, and F, portions of trunks of different species. 

 E, a spore-bearing cone. G, section of part of cone, showing sporophylls, spore chambers, 

 and spores. H, a piece of one of the stigmaria, or subterranean branches, from which the 

 true roots issued, as shown by the root scars. {Modified from Turtox chart, courtesy General 

 Biological Supply House, Inc.) 



the gymnosperms and angiosperms together make up the division 

 Spermatophyta. 



The Ferns (Filicinae) are said to have some 8,000 living species, most of 

 which fall into the order Filicales, or true ferns. We have already discussed their 

 structure and mode of reproduction in Chaps. XIII and XVII and will not repeat 

 what was given there. As a group the ferns are widely distributed but are most at 



