FILICES 91 



The family of Schizaeace^e comprises a small number of species, in- 

 cluded in five genera, of which Mohria(Sw.)and Trochopteris (Gardn.)are 

 monotypic. Aneimia (Sw.) and Schizaea (Sm.) resemble the Osmundaceae 

 in their paniculate appearance. All the species of Lygodium (Sw.) pre- 

 sent the appearance of climbing stems, from the peculiar structure and 

 mode of growth of the leaves already described. The family is confined 

 to the warmer parts of the globe. 



Literature. 



Prantl — Untersuchungen zur Morphologic der Gefasski^'ptogamen, Heft 2, iSSi ; 

 also in Engler's Jahrb. i88i, p. 297. 



Order 7. — Marattiace^. 



The Marattiaceae differ more widely from the typical ferns than any 

 of the families hitherto described, and are by many authorities separated 

 from them into a distinct class. But the point of divergence most relied 

 on, the endogenous origin of the sporanges, has lost much of its signifi- 

 cance since it has been known that the Osmundaceae and Schiz^aceae 

 present connecting links in this respect. The aerial flat prothallium, 

 the circinate vernation and general structure of the leaf, and the ultimate 

 structure of the sori, present so many points of contact with the other 

 orders of Filices, that it seems most desirable at present to retain them 

 as an aberrant order of the class. 



The prothallium, the development of which is very slow, is a dark 

 green elliptical or heart-shaped plate of tissue, lying on the surface of 

 the soil, consisting of one or more layers of cells, and with a projecting 

 hemispherical cushion on the under side. Its development has been 

 followed out in Marattia (Sm. ) and Angiopteris (Hoffm.). Chlorophyll is 

 formed in the spore as soon as it begins to germinate. The exospore 

 bursts, and the first cell of the prothallium projects as a papilla between 

 the two lobes. After a considerable time the first division takes place 

 at right angles to the direction of growth, and the first rhizoid is formed. 

 Further divisions follow rapidly, and the prothallium soon becomes a 

 cellular tissue, and is distinguished from that of typical ferns by its deep 

 green colour and by its moderately thick cuticle. One of the cells first 

 formed becomes an apical cell, from which fresh cells are formed until 

 the prothallium has assumed its ultimate cordate form. The antherids 

 make their appearance, after a period of some months, on both sides of 

 the prothallium, but especially on the ventral cushion. Their structure 

 differs in some respects from that of typical ferns. From a single 

 superficial cell are produced a central cell, two upper cells, and a 

 triangular stigmatic cell, which is thrown off when the antherid is 



