Fig. 21 



Osmunda: a, partly fertile frond of O. regalis; b, stele of O. 

 cinnamomea; c, prothallus of O. Claytoniana; d, antheridium ; 

 E, archegonium; g, sporangium. Leptopteris: f, fertile pinnule 

 of L. hymenophylloides. Todea: h, fertile frond of T. barbara; 

 I, J, sporangial primordia (i with tetrahedral archesporial cell, 

 J with cubical archesporial cell) ; k, stele 



(a, f, h, after Diels; c-e, Campbell; g, Luerssen; i, J, Bower; 

 K, Seward and Ford) 



other two genera, the three genera are so similar in other 

 respects that they are, without doubt, closely related, and 

 this conclusion is supported by chromosome counts. The 

 haploid number is n = 22 throughout. 



Filicales 



In the past, the name FiHcales was applied in the broadest 

 possible sense, so as to include all the ferns but, recently, its 

 use has been restricted, and it is applied just to the homo- 

 sporous leptosporangiate ferns (as in Engler's Syllabus der 



145 



