GROUP III. PTERIDOPHYTA : FILICINJI ; EUSPORANGIATJ!. 383 



palmately-lobed sterile fronds. B )trychium is represented in the British Flora 

 by B. Lunaria (the Moon-wort) which occurs in hilly districts. Helmin- 

 thostachys includes the single species H. zeylanica which occurs in the Eastern 

 tropics. 



Order 2. Marattiaceae. This order includes the genera Marattia, Angio- 

 l>teris, Kaulfussia, and Danaea, none of which are European, but are mainly 

 tropical. 



SPOROPHYTE. In its general morphology the sporophyte agrees with that of 

 the Ophioglossacese ; but the leaves are more numerous, much larger, compound, 

 and circinate in vernation, and each bears a pair of stipules. Branching of the 

 stem occurs only in Danaea ; in Kaulfussia the stem is a subterranean, creeping, 

 dorsiventral rhizome. The roots are somewhat fleshy, and are much branched. 

 The apical growing-point of both root and stem consists of a group of a few (four 

 or more) initial cells. The eporophylls are not differentiated into a sterile and 

 a fertile portion, but have the appearance of foliage-leaves. The numerous 

 sporangia are borne in sori on the ribs of the under surface of the sporophyll ; 

 in Angiopteris the sporangia of a sorus are free, whilst in all the other genera 

 they are coherent, forming a synangium (see p. 72 and p. 375). The sporangia 

 are not embedded in the placenta; they are generally sessile, but the synangium 

 is sometimes (Marattia, sect. Eupodium) shortly stalked ; they have no an- 

 nulus; they dehisce generally by a longitudinal slit on the inner side, but in 

 Danaea by a single apical pore; the wall of the mature sporangium consists of 

 several layers of cells. The archesporium is the terminal hypodermal cell of 

 the axile row of cells of the young sporangium. The spores are numerous, and 

 are either tetrahedral or radial. 



The stem is polystelic ; the arrangement of the phloem- and xylem-bundles 

 of stem and leaf is completely concentric ; there is no well-marked endodermis, 

 except in Danaea; there is no sclerenchyma in Angiopteris, and in the other 

 genera (except Danaea) it is not so well developed as in the leptosporangiate 

 Ferns ; the tissues are penetrated by lysigenous gum-passages. 



The embryology of the sporophyte is known in Angiopteris and Marattia. 

 The oospore divides by a basal wall which is transverse to the long axis of the 

 archegonium ; octants aro then formed, as in the leptosporangiate Ferns ; from 

 the epibasal octants (furthest from the neck of the archegonium) arise the 

 primary leaf (cotyledon) and stem ; from the hypobasal octants (next the neck 

 of the archegonium) arise the foot and the primary root ; the cotyledon grows 

 straight upwards and penetrates the tissue of the prothallium overlying it. 



GAMETOPHYTE. On germination the spore gives rise to a dorsiventral green 

 prothallium, which begins as either a plate or a mass of ceils, and only rarely 

 (under abnormal conditions) as a filament ; it grows by an apical cell, and pro- 

 duces root-hairs posteriorly. A projecting cushion of tissue, representing a 

 gametophore, is developed on the under surface in the median line ; it produces 

 first antheridia and then archegonia, so that, in a fully-developed prothallium, 

 the antheridia are on the posterior and the archegonia on the anterior portion 

 of the gametophore ; some antheridia are, however, also developed on the 

 upper surface of the prothallium ; the antheridia are completely, the arche- 

 gouia almost completely, sunk in the tissue. The neck canal- cell generally 

 divides transversely into two. 



