GLEICHENIACEAE 



561 



be the final decision on this point, it is clear that sori of the same type 

 as those of Gleichenia existed at the Carboniferous period, and that in size 

 and form the constituent sporangia were like those seen in the living 

 species. 



ANATOMY. 



There is greater uniformity of anatomical structure in the Gleicheniaceae 

 than in the Schizaeaceae ; but still there are marked differences within 

 the family which have a probable phyletic bearing when placed in relation 



FIG. 313. 



A diagram of the tissues of the rhizome of Gleichenia Jlabellata. X 8. B = section of 

 the stele (somewhat diagrammatic) of G. pectinata. X 26. C = part of the stele of G. 

 dichotoma. X 350. (All after Boodle, from Campbell's Mosses and Ferns.") 



to other characters. 1 In the majority of species the rhizome shows in 

 ;he internodes a centrally placed, solid stele (protostele), consisting of a 

 central mass of xylem composed of tracheides and parenchyma, and 

 surrounded by a continuous ring of phloem, pericycle, and endodermis 

 'Fig. 313 A). There is thus a general resemblance to the structure of the 

 rhizome of Lygodium ; but a point of difference is that whereas in Lygodium 

 there is no typical protoxylem, in Gleichenia the protoxylem is represented 

 ay several distinct groups of spiral elements, which are mesarch. The 

 tracheides of the xylem are arranged in chains and groups separated by 

 parenchyma : in fact the structure as seen in G. flabellata is strikingly 

 ike that of Lygodium, except in the matter of the protoxylem. In several 



*The data here embodied are chiefly derived from Poirault, Ann. Set. Nat. Bot.> 

 7 Serie, T. xviii., p. 170, etc., and from Boodle, Ann. of Bot., vol. xv., p. 703. 



2 N 



