[752] Gwynne-Vaughan (05).
[753] Hooker and Baker (68) p. 440.
[754] The term synangium is applied to sporangia more or less completely united with one another and producing spores in groups separated by walls of sterile cells. A synangium may be regarded as a spore-forming organ produced by partial sterilization of sporogenous tissue or as a group of coalescent sporangia.
[755] Brebner (02); Rudolph (05).
[756] Tansley (08) p. 90; Kühn (90).
[757] Pelourde (08) has recently dealt with the anatomy of recent and fossil Marattiaceous ferns.
[758] Copeland (08) Pl. I. (09) Pl. V.
[759] Bower (96).
[760] Jeffrey (98). For an account of the anatomy of Helminthostachys, see Farmer and Freeman (99).
[761] Stur (75) A. p. 77, Pl. XI. fig. 8.