. Un manual de botánica criptogámicas. Cryptogams. 74 CRYPTOGAMS VASCULAR, el desarrollo de la fértil parenchyme (apical) parte de las hojas, dando la apariencia de un thyrsoid panicled o inflorescencia. La sf naranja suele ser azotado, y tiene una forma elíptica, o de una batalla- dore o raqueta-bat. Los lados son comúnmente delgado y membranoso y- la sporange dehisces bien longitudinalmente o transversalmente, generalmente a partir de la elasticidad de una corona o anillo de células de paredes gruesas marrón que corre a lo largo de o a través de ella. La posición de este anillo, y su desarrollo más o menos completa o

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. A handbook of cryptogamic botany. Cryptogams. 74 VASCULAR CRYPTOGAMS development, the parenchyme of the fertile (apical) part of the leaf, giving the appearance of a panicled or thyrsoid inflorescence. The sf orange is usually stalked, and has an elliptical form, or that of a battle- dore or racket-bat. The sides are commonly thin and membranous, and- the sporange dehisces either longitudinally or transversely, generally from the elasticity of an annulus or ring of brown thick-walled cells running along or across it. The position of this annulus, and its more or less complete development or entire absence, are useful characters in the subdivision of the class. In the Marattiaceae the sporanges are of altogether different origin, being developed from h)rpodermal masses of cells; and transitional forms occur between the two. The spores are minute, very commonly re- niform, or often nearly cubical, resembling pollen- grains in structure, usually furnished with two coats, an eocospore and endospore, the latter of which is some- times double, and the former generally marked with papillse, reticulations, &c. A more minute descrip- tion must now be given of the structure and peculi- arities of the various organs. The great distinguishing feature which characterises the development of the stem of ferns, as contrasted with that which occurs in all Flowering Plants (Gym- nosperms and Angiosperms), is the presence of a single apical cell, from which the whole of the growing point or apical meristem origi- nates, and which may therefore be recognised as the parent-cell of the whole of the tissue subsequently formed. This apical cell is usually wedge-shaped in creeping stems with a bilateral structure, a three-sided pyramid in erect or ascending stems. The growing apex of the stem is frequendy completely hidden in the youngest leaf-bud, but in other species' there is a considerable intervening space. In some Hymenophyllacese leafless prolongations of the stem assume the ap