372 



BOTANY. 



Pig. 866.— Prothalllum and young plant of Adi- 

 antum CapUlus-Veneris, seen in vertical longitudinal 

 section. ^,^, the prothallium ; a, archegonia : h, root- 

 hair ; E, the young plant ; w, its first root ; 6, its first 

 leaf. X about 10.— After Sachs. 



490. — The Pilicinse may be here arranged iiiider four 



orders, as follows :* 

 /. IsosporecB. — 

 Spores of one 

 kind. 



Order 1. rilioes, 

 the true Ferns. 

 Sporangia compos- 

 ed of modified tri- 

 cViomes, each de- 

 veloped from a sin- 

 gle epidermal cell, prodnced in clusters on the surface of or- 

 dinary or slightly modified 

 leaves. Each sporangium 

 with an elastic ring. No stip- 

 ules. 



Order 2. Marattiaeese, the 

 Eingless Ferns. Sporangia 

 produced from a group of epi- 

 dermal cells ; the ring either 

 rudimentary or wanting. The 

 large, much -branched leaves 

 with stipules. 



Order 3. Ophioglossacese, 

 the Adder-Tongues. Sporan- 

 gia formed by groups of cells 

 in the interior of a modified 

 branch of the sheathing leaf. 

 The ring is absent. 



//. HeterosporecB. — Spores 

 of two kinds. 



Order 4. Rhizocarpese, the 

 Pepperworts. Sporangia com- 

 posed of modified trich- 

 omes (?); the microsporangia 

 containing many microspores. 



Fig. 257. — A, a transverse section of 

 the stem (rhizome) of Pteris aquUina, 

 slightly enlarged, r, brown sclerenchy- 

 ma, forming a hard c heath beneath the 

 epidermis ; p, colorless parenchyma of 

 the fundamental system ; ig, inner fibro- 

 vascular bundles ; Off, the broad upper 

 band of the outer bundle zone ; pr, a 

 band of elongated thick-walled cells, 

 sclerenchyma or fibrous tissue— a second 

 one occurs on the other side of the cen- 

 tral bundles. S, the separated .upper 

 fibro-vnscular bundle of tne stem (rhi- 

 zome), St, and its branches, si', «<" ; ft, 

 bundles of the leaf stalk ; «, «, u, out- 

 line of the stem. — After Sachs. 



* This arrangement is essentially that modification of Saclis' pro- 

 posed by Professor McNab. See his " Outlines of the Classification of 

 Plants," American edition, Chapter VII, 



