526 SELAGINELLACEJE. [Selaginella. 



than the branch ; scales erect or spreading, broader and longer than the 

 leaves, with long spinulose teeth. Microspores echinate, in 2-valved reni- 

 form capsules. Macrospores globose, in 3-4-valved and lobed capsules. — 

 Distrib. N. and W. Europe, Siberia, Himalaya, N. America. 



2. ISOETES, L. Quill wort. 

 Aquatic or terrestrial stemless plants. Corm depressed. Leaves long, 

 subulate or filiform, often tubular and septate, base sheathing. Capsules 

 sessile in the axils of the leaves, partially enclosed by and adnate to their 

 sheathing bases, traversed by cellular threads ; those of the outer leaves 

 contain globose macrospores, those of the inner contain oblong 3-gonous 

 microspores. Macrospores with a crustaceous coat, marked on the upper 

 hemisphere with 3 radiating lines, and bursting by 3 valves. — Distrib. 

 Chiefly N. temp, and warm regions ; species 6 or 8. — Etym. icros and eros, 

 ever-green ; of obscure application. 



1. I. lacus'tris, L. ; aquatic, leaves subulate, macrospores covered 

 with crested ridges or tubercled. 



Bottoms of alpine and subalpine lakes, from Caithness to Salop and N. 

 Wales ; ascends to 2,000 ft. in the Highlands ; Ireland ; frt. May-July. — 

 Corm often as big as a hazel-nut. Leaves 10-20, 2-6 in., rigid, obscurely 

 4-gonous, dark green, of 4 septate tubes. Capsule ovoid or globose, 

 partially covered by the inflexed edges of the sheath. Macrospores tuber- 

 cled by the protrusion of the inner wall through perforations of the outer. 

 Microspores granular. — Distrib. Europe (Arctic) N. of the Alps, W. 

 Siberia, N". America. 



I. lacus'tris proper ; leaves erect green, capsules § covered by the edges of 

 the leaf-sheath, tubercles of macrospore short. — Tar. I. More'i, Moore ; 

 leaves 18 in. long. In deep water, Wicklow. 



I. echinospo'ra, Durieu ; leaves spreading paler, capsules almost enclosed in 

 the leaf-sheath, tubercles of macrospore longer more acute. — N. "Wales, 

 Aberdeen, Dumbarton, Kerry. 



2. I. Hys'trix, Durieu ; terrestrial, leaves filiform, macrospores ob- 

 tusely tubercled. I. Duriodi, Hook, 



Sandy soil, inundated at times, Guernsey; frt. May-June. — Corm short, 

 stout, subglobose, 1 in. diam., clothed with the old spinescent dark 

 horny leaf-bases, which consist of lateral subulate processes, and an inter- 

 mediate tooth. Leaves 1-2 in., slender, plano-convex, obscurely tubular, 

 sheath enveloping the capsule. Macrospores white. — Distrib. S. Europe, 

 N. Africa. 



Order XCI V.— MARSILEA'CEJE. 



Aquatic plants of various habit. Rootstock or stem creeping. Leaves 

 filiform or bearing 4 obovate leaflets ; vernation circinate. Fructification 

 of 2- or more-celled coriaceous oblong or globose capsules (formed of a meta- 

 morphosed leaf) placed near or on the rootstock, and containing on parietal 



