372 



BOTANY. 



f'l 



Fig. 256. Prothallium and young plant of 

 antum Capillus-Veneris, seen in vertical longitudinal 

 section. p,p, the prothallium ; , archegonia : h, root- 

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

 leaf. X about 10. After Sachs. 



490. The Filicinae may be here arranged under four 



orders, as follows :* 

 /. Isosporece. 

 Spores of one 

 kind. 



Order 1. Filices, 

 the true Ferns. 

 Sporangia compos- 

 ed of modified tri- 

 chomes, each de- 

 veloped from a sin- 

 "^V****- gle epidermal cell, produced in clusters on the surface of or- 

 , dinary or slightly modified 

 leaves. Each sporangium 

 with an elastic ring. No stip- 

 ules. 



Order 2. Marattiacese, the 

 Bingless 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. Ophioglossaceae, 

 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. 



//. Heterosporete. Spores 

 of two kinds. 



Order 4. Ehizocarpese, 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 aquilina, 

 slightly enlarged, r, brown sclerenchy- 

 ma, forming a hard sheath beneath the 

 epidermis ; p, colorless parenchyma of 

 the fundamental system ; ig, inner fibro- 

 vascular bundles ; ag, 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. B, the separated upper 

 fibro-vascular bundle of the stem (rhi- 

 zome), st, and its branches, st', st" ; b, 

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

 line of the stem. After Sachs. 



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

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

 Plants," American edition, Chapter VII. 



