373 



BOTANY. 



490. — The Filicinse may be liere arranged under four 



orders, as follows :* 

 /. IsosporecB. — 



I^'^£lrrWf^f!tmw!mSKi''n ^i' Spores of one 



kind. 

 Order 1. Pilioes, 



the true Ferns. 



Sporangia compos- 

 Fig. 256.— Prothalliam and young plant of Adi- j „ j'C j 4- • 

 antum Capillus-Veneris, seen in vertical longitudinal 60. 01 niOulueu tri- 

 Bection. p,j), the prothallium ; a, archegonia : A, root- „i__,„„ oonV. ^a 

 hair ; ^, the young plant ; w, its first root ; ft, its first cnoineb, eauii ue- 



leaf. X about lo.-After Sachs. veloped from a sin- 



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. Marattiaceee, the 

 Eingless Terns. 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. 



II. Heterosporem. — Spores 

 of two kinds. 



Order 4. Rhizocarpeae, the 

 Pepperworts. Sporangia com- 

 posed of modified trich- 

 omes (?); the microsporangia 

 containing many microspores, 



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

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

 Plants," American edition, Chapter VII. 



Kg. Wt.—A, a transverse section of 

 the stem (rhizome) of Pteris aguilina, 

 slightly enlarged, r, brown sclerenchy- 

 ma, forming a hard bheath 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 ; ^r, 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" ; 6, 

 bundles of the leaf stalk ; w, z/, m, out- 

 line of the stem.— -After Sachs. 



