1907] 



BINFORDSPORANCIUM OF LYGODIUM 



215 



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of the leaf (figs. 7, 2). The sporangia arise in acropetal succession on 

 the margin of the lacinia (fig. j). The initial cell of the sporangium 

 appears as a marginal cell near the apex of the pinnule; and at first 

 it projects obliquely outward and forward. The indusium arises, 

 from the edge and ventral surface of the pinnule basal to the sporan- 



Fig. I, Two pinnules bearing sporangia (ventral surface). X13. — Fig. 2. Dor- 

 sal surface of a pinnule. X 13. — Fig. 3. A longitudinal section of a pinnule showing 

 the sporangia. — Fig. 4. A longitudinal section of a pinnule showing the apex and an 

 early stage in the development of a sporangium and induslum. 



gium (fig. 4). The growth of the indusium out from the edge of the 

 pinnule carries the base of the sporangium out, as shown in fig^3^ so 

 that it projects forward or slightly in toward the costa. The part of 

 the indusium which arises from the ventral surface grows out and for- 

 ward so as to cover the sporangium on the ventral side, but on the 

 dorsal side it is exposed for some time (figs. 5, 6). Later a forward 

 growth of lamina incloses the sporangium (fig. j), and carries its base 

 forward so that it projects in a ventral direction. It has thus beea 



m- 



