208 



THE MARATTIALES 



rangiophore in all of the living Ophioglossaceae is adaxial, while in the Marattiaceae 

 the synangia are abaxial, is a serious objection to such a hypothesis; and the most 

 plausible explanation at present seems to be that of a progressive sterilization of 

 part of the sporophyll itself and the expansion of the sterile tissue into the broad 

 lamina of the leaf bearing the separated sporangia or synangia upon its lower surface. 

 It must be admitted that the difference between the sporophylls of the existing 

 Marattiaceae and those of the Ophioglossaceae is very great, and the leaves of the 

 former, superficially at least, are much more like those of the leptosporangiate ferns; 

 but the sporangia themselves are very similar in their development to those of the 



A. Lower surface of a sporophyll of Kaulfussioj showing 



circular synangia. X1.5. 

 6. Median section of a synangium. X12. 



C, D. Cross-sections of a synangium. 



C, Near top. showing openings of loculi. 



D. Near middle. X12. 



Ophioglossaceae, and offer no obstacle to the assumption of a fairly close relationship 

 between the Ophioglossaceae and the Marattiaceae, which is indicated by the history 

 of the development of the gametophyte, and the vegetative organs and tissues of the 

 sporophyte. Perhaps the most marked difference between the tissues of the Marat- 

 tiaceae and the Ophioglossaceae is the prevalence of the mucilage ducts in the tissues 

 of Marattiaceae, but these arise rather late in the history of the sporophyte, and it is 



Fig. 1 89. — Danaa jamaicensis* 



A. Base of a fertile leaflet, showing synangia, sp. Xi. 



B. Transverse sections of three synangia. X12. 



C. Horizontal section of a synangium. 



significant that they are less developed in the presumably more primitive Kaulfussia 

 than they are in the more specialized types like Angiopteris. Another difference is 

 the deyeloprnerit of sclerenchyma, which is quite absent from the Ophioglossaceae; 

 but this again is also quite absent from Kaulfussia, which, on the whole, must be 

 considered to be the most primitive of the living Marattiaceae and also the form 

 which most closely approaches the Ophioglossaceae. 



