VIII 



MARATTIALES 



299 



Marattia includes about twelve species of tropical and sub- 

 tropical Ferns, both of the Old World and the New. Kaiil- 

 fiissia includes but a single species, belonging to southeastern 

 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. Kaitl- 

 fussia 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. 



Fig. 170. — Datiwa alata. A, Sterile; B, fertile pinna, X i '/4 ; C, cross-section near the 

 base of the petiole, X6; set, selerenchyma; m, mucilage ducts; vb, vascular bundles. 



The genus Dancea is exclusively American and comprises 

 about fourteen species of small or middle-sized Ferns. D. sim- 

 plicifoUa has a simple lanceolate leaf, the others have once- 

 pinnate leaves. The fleshy stipe is often characterised by con- 

 spicuous swellings. The venation of the leaves (Fig. 170) is 

 much like that of Angioptcris and some species of Marattia. 

 The fertile pinnae are decidedly contracted, and the elongated 

 synangia almost completely cover their lower surface. 



The stem (Fig. 169) is a horizontal fleshy rhizome, the 

 leaves arranged in two ranks upon the upper side. The leaf- 



