404 



BOTANY 



of Polypodium vulgare are also orbicular, but they have no indusia. In 

 the common Brake, Pteris aquilina, the sporangia form a continuous 

 line along the entire margin of the leaf, which folds over and covers 

 them with a false indusium. 



The sporangia of the Cyatheaceae, to which family belong principally the tree- 

 like Ferns, are characterised by a complete annulus extending obliquely over the 

 apex of the capsule (Fig. 335, B). The Eymenophyllaceae, often growing as 



Fig. 335. — Sporangia (magnified). A, Of Osmunda regalis, dorsal view (after Luerssen) ; B, of 

 Alsophila compta ; C, of Aneimia rutaefolia. (After Martius.) 



epiphytes on Tree-Ferns, have also sporangia, with a complete, oblique, or horizontal 

 annulus. The sporangia of the ScMzaeaceae, on the other hand, have an apical 

 annulus (Fig. 335, 0), while in the Osmundaceae, of which the Royal Fern, Osmunda 

 regalis, is a familiar example, the annulus is represented merely by a group of thick- 

 walled cells just below the apex of the sporangium (Fig. 335, A). 



Ferns, like those just referred to, in which each sporangium is 

 developed from a single epidermal cell, are classed together as Filkes 

 leptosporangiatae, in distinction to the Eusporangiatae, in which the 

 sporangia take their origin from a group of epidermal and underlying 



cells. The Eusporangiatae comprise the 

 two families Marattiaceae and Ophio- 

 glossaceae. 



The Marattiaceae are tropical Ferns, with 

 thick, tuberous stems and gigantic fronds, each 

 with two stipules at the base. Their mature 

 sporangia are provided with a stiff and firm 

 many-layered wall, and are either free (Angi- 

 opteris), or all the sporangia of a sorus are 



united in an oval, capsule-like body, divided 

 Fig. SSe.-mrattia luvis Sporangia! intQ a c0rresp0Ilding number „ f ohambers 

 sorus; A seen from the side; B r ° 



opened, showing the chambers, (x \* l B- ««>b;. 



12.) The Ophioglossaceae include but few species. 



Examples of this family are afforded by Ophio- 

 glossum vulgatum, Adder's Tongue, and Botrychium, Moonwort (Fig. 337). Both 

 have a short stem, from which only a single leaf unfolds each year. The leaves 

 in both cases, are provided with leaf-sheaths, and peculiarly divided into fertile 



