26 GYMNOSPERMS 



found the seed, Tn'gonocarpus, on the leaf of Ncuroptcris; and David 

 White found seeds of a Carboniferous form which he called Anci- 

 mites fertilis. 



With such a start the work went on rapidly and seeds were found 

 on so many of the supposed ferns that it began to look as if these 

 primitive seed plants, rather than the ferns, were the dominant fern- 

 like plants of the Carboniferous. 



Fig. 23. — Trigonocarpus: contained in coal ball found in strip mine of Sunlight Coal 

 Company, near Evansvillc, in southern Indiana; natural size. 



Of course, there were true ferns in the Carboniferous, both homos- 

 porous and heterosporous, and they were probably abundant. Not 

 all of the ferns became heterosporous, and not all of the heterospo- 

 rous ferns advanced to the seed stage. They remained ferns and the 

 ferns of today have come from them by direct descent. 



The most intensive work has been done in Great Britain, with 

 Williamson, Kidston, Oliver, Scott, Seward, and more recently 

 Gordon and H. H. Thomas, Walton, and Harris as the most 

 prominent investigators. Scott, not being burdened with a teaching 

 position, has made this study his life-work, and in addition to his 

 research papers, has presented the whole subject in his book. Studies 



