274 MOSSES AND FERNS chap. 



The former genus includes seven species -^ belonging to the 

 tropics of both the old and new world. The latter includes but 

 a single species, belonging to south-eastern Asia. The synangia 

 are scattered over the lower surface of the palmate leaf, and are 

 circular, with a central space into which the separate loculi open 

 by a slit, as in Marattia. Kaulfussia is characterised by very 

 large pores upon the lower side of the leaf. A study of the 

 development of these shows ^ that at first they are perfectly 

 normal in form, and that the large round opening is a secondary 

 formation, the two guard cells of the young stoma being torn 

 apart, and disappearing almost entirely in the older leaf 



III. The Danseaceae. The single genus DancEa includes 

 eleven species, according to Hooker,^ all confined to the new 

 world. They are Ferns of moderate size, with simple or pin- 

 nate leaves, whose venation is like that of Angiopteris. The 

 synangia are long, and frequently extend completely from the 

 midrib to the margin of the leaf. They are like those of 

 Marattia, but open by a terminal pore instead of by a slit. 

 Between the synangia the tissue of the leaf in some species 

 forms an elevated ridge, with the top broader, so that the section 

 is T-shaped. 



Fossil MarattiacecE 



It has been shown ^ that the majority of the earlier fossil 

 Ferns belong to this order, and of the living families the 

 Angiopterideae and Dana^aceae have also representatives in a 

 fossil condition. The Marattieae and Kaulfussieae are only 

 known in a living state. Five families, on the other hand, 

 contain only fossil forms, some of which appear to be in certain 

 respects intermediate between the Marattiaceae and some of the 

 leptosporangiate Ferns.^ 



The Isoetacece 



The systematic position of this extremely isolated group 

 has been long a debated question. Most botanists assign it a 

 place near the Lycopodineae, but there are serious objections to 

 this, and it seems to the writer that at present the weight of 

 evidence is in favour of placing Isoetes with the eusporangiate 



^ Hooker ( I ). - Luerssen (i). " Hooker (i). 



^ Solms-Laubach (2), p. 143. ^ Solms-Laubach, I.e. p. 148. 



