310 MOSSES AND FERNS CHAP. 



The production of secondary sporophytes as adventitious 

 buds upon the sporophyte is a regular occurrence in some 

 species. Asplenium bulbiferum and Cystopteris bulbifera are 

 familiar examples of such sporophytic budding. In these large 

 numbers of buds are formed which soon develop all the charac- 

 ters of the perfect sporophyte. Very early a definite apical cell is 

 established from which all the other parts are derived. In 

 Camptosorus rhizophyllus, the " walking fern" of the Eastern 

 United States, a single bud is formed at the tip of the slender 

 leaf which bends over until it takes root. From this terminal 

 bud another leaf grows and roots in the same way. 



Classification of the Leptosporangiatce 



The Leptosporangiatse fall into two groups, which may be 

 termed orders, although the two families in the second order 

 (Hydropterides) are not closely related to each other, but each 

 has nearer affinities with certain of the homosporous forms. 



' I. Homosporous Ferns with large green prothallium, usu- 

 ally in its early stages growing from a single apical cell ; more 

 commonly monoecious, but sometimes dioecious. Leaves always 

 circinate in vernation. Sporangia with a more or less de- 

 veloped annulus, either borne upon ordinary leaves or on 

 specially modified sporophylls. Usually, but not always, each 

 group of sporangia (sorus) covered by a special covering, the 

 indusium. 



Order I. Filices. (Eufilicineae. Sadebeck (7)). 



Family i. Osmundacese. 



Family 2. Gleicheniacese. 



Family 3. Matoniacese. 



Family 4. Hymenophyllaceae. 



Family 5. Schizaeaceae. 



Family 6. Cyatheacese. 



Family 7. Parkeriaceae. 



Family 8. Pplypodiacese. 



II. Heterosporous forms, either aquatic or amphibious ; the 

 prothallia are always dioecious, the female prothallium with 

 chlorophyll and capable of more or less independent growth 

 when not fertilised ; male prothallium always without chloro- 

 phyll, the vegetative part reduced to one or two cells, besides 

 the antheridium. Leaves either circinate (Marsiliaceae) or 



