VASCULAR CRYPTOGAMS. 195 



tissue of the prothallium. The species are all homosporous. The sporophyte is a 

 simple, usually unbranched, often tuber-like, erect or obliquely growing stem, with 

 leaves in spirals one close above another ; in most Ophioglosseae one only unfolds 

 each year. The leaves are very large in proportion to the stem and usually much 

 branched, and in the Marattiaceae they have commonly at their bases thick fleshy 

 excrescences, which may be compared to the stipules of the higher plants but which 

 are wanting in some species, as in Danaea, and in the Ophioglosseae. The sporangia 

 arise on the under side of ordinary foliage leaves, or on sporophylls which form 

 spikes or panicles ; they are either sunk in the tissue of the sporophyll, as in 

 Ophioglossum, or project above it as spherical capsules that are sometimes amalga- 

 mated with one another. 



II. EQUISETINEAE. 



A. HOMOSPOROUS EQUISETINEAE : Equisetaceae (and Calamites). The spores 

 are of one kind and produce prothallia which live independently and are usually 

 dioecious, the female being larger, the males smaller. The sporophyte is a copiously 

 branched stem, with distinctly articulated internodes and with proportionately small 

 and sheathing whorls of leaves ; the branches also are in whorls, and spring from 

 the nodes of the stem in strict acropetal succession ; a root which branches mono- 

 podially may be given off beneath each branch. The sporangia are formed as 

 pluricellular protuberances on peltate leaves (sporophylls) which form a terminal 

 inflorescence (spike) ; there are from five to ten sporangia on each leaf ; the mother- 

 cells of the spores are produced from a unicellular hypodermal archesporium. Stem 

 and root have a large apical cell which gives off three rows of segments. The 

 vascular bundles of the stem are disposed in a circle ; like the bundles of Monocoty- 

 ledons they contain little xylem. The axile bundle of the root has no pericambium. 



B. HETEROSPOROUS EQUISETINEAE (fossil forms only). Macrospores and micro- 

 spores have been found, but their germination is of course unknown. The sporophyte 

 is a copiously branched stem divided into very distinct internodes, with whorls of 

 linear or lanceolate leaves which are not united into a sheath. The branches 

 are either in whorls like the leaves, or in two rows (Annularia). The inflorescences * 

 are composed of alternating whorls of fertile and sterile leaves. 



1. Annularieae. 



2. Asterophylliteae. 



III. SPHENOPHYLLEAE. 



Known only in the fossil state, and heterosporous ; the sporangia are seated on 

 the base or in the axil of the leaf, as in Lycopodiaceae. The leaves with frequently 

 bifurcate nerves radiating from a common base are in whorls on the nodes of the 

 stem, in the centre of which is a triarch bundle of tracheids. 



IV. LYCOPODESTEAE. 



The prothallia spring either from spores of one kind and are independent and 

 monoecious, or from spores of two kinds, macrospores and microspores, and then the 



1 Whether these really belong to the Annularieae or Asterophylliteae is not certainly ascertained. 



O 2 



