3o6 MOSSES AND FERNS chap. 



directly from the sporophyte without the intervention of spores, 

 is known in a number of species, and has been especially 

 investigated by Bower/ He found that there were two types 

 of apospory, as he named the phenomenon, one where the 

 prothallium was produced from a sporangium arrested in its 

 normal growth, and by active multiplication of the cells of the 

 stalk and capsule wall formed a flattened structure, which soon 

 showed all the characters of a normal prothallium with sexual 

 organs. In the second case the prothallia grew out directly 

 from the tips of the pinnas, and there was no trace of sporangia 

 being formed previously. The first observation of these 

 phenomena were made upon two garden varieties, Athyriumfilix- 

 foemina var. clarissima and Polystichuni angulaj'e var. pulcherri- 

 mum, but since, Farlow ' has discovered the same phenomenon 

 in Pteris aquilina. In the latter the prothallia were always 

 transformed sporangia. 



The production of secondary sporophytes as adventitious 

 buds upon the sporophyte is a regular occurrence in some 

 species. Aspleniuin bulbiferuni and Cystopteris bulbifera are 

 familiar examples of such sporophytic budding. In these large 

 numbers of buds are formed which soon develop all the 

 characters of the perfect sporophyte. Very early a definite 

 apical cell is established from which all the other parts are 

 derived. In Cainptosamms rJiizopJiyllus, 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 

 w^ay. 



Classification of the LeptosporangiatcB 



The Leptosporangiatae fall into two groups, which may be 

 termed orders, although the two families in the second order 

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

 has nearer affinities with certain of the homosporous forms. 



I. Homosporous forms with large green prothallium, usually 

 in its early stages growing from a single apical cell, more 

 commonly monoecious but sometimes dicecious. Leaves always 

 circinate in vernation. Sporangia with a more or less developed 

 annulus, either borne upon ordinary leaves or on specially 

 1 Bower (6). 2 Farlow (2). 



