PTERIDOPHYTA. 2/ 



3. Selaginella apus (L.) Spring. (I. F. f. 101.) Annual, light green, stems 

 Creeping, 2.5-10 cm. long, much branched, flaccid, angled on the face. Leaves 

 minute, membranous, of 2 kinds, 4-ranked, spreading in 2 planes : upper leaves of 

 the lower plane spreading, the lower reflexed, ovate, acute, serrulate, not distinctly 

 ciliate ; leaves of the upper plane ovate, short-cuspidate ; spikes 6-16 mm. long, 

 obscurely quadrangular ; bracts ovate, acute, sometimes serrulate, acutely keeled in 

 the upper half ; macrosporanges more abundant toward the base of the spike. In 

 moist shaded places, often among grass, Me. and Ont. to the N. W. Terr., south to 

 Fla., La. and Tex. 



Family 3. ISQETACEAE Underw. 

 Quillwort Family. 



Aquatic or marsh plants rooting in the mud, with a short buried 2- 

 lobed or 3-lobed trunk (stem) sending out abundant roots and sending up 

 a compact tuft of rush-like leaves. Sporanges sessile in the axils of the 

 leaves, some containing macrospores (macrosporanges), others micro- 

 spores (microsporanges) ; the former germinate into prothallia bearing 

 only archegones, the latter into prothallia bearing usually only a single 

 antherid. The family consists of the following genus only. 



i. ISOETES L. QUILLWORTS. (See Appendix.) 



Submerged, amphibious or uliginous plants with a cluster of elongated awl- 

 shaped leaves rising from a more or less 2-3-lobed fleshy short stem, the leaves with 

 or without peripheral bast-bundles, with or without stomata, bearing a small 

 membranous organ (ligule) above the base. Sporanges sessile in the excavated bases 

 of the leaves, orbicular or ovoid, the sides more or less covered with a fold of the 

 inner side of the leaf-base (velum). The sporanges of the outer leaves usually con- 

 tain spherical, mostly sculptured macrospores, those of the inner ones contain minute 

 powdery usually oblong microspores. [Name Greek, taken from Pliny, apparently 

 referring to the persistent green leaves.] About 50 species, widely distributed. 

 Owing to their aquatic habitat and apparently local distribution, these plants are 

 popularly little known. 



Submerged or rarely emersed in very dry seasons ; leaves quadrangular, without peripheral 



bast-bundles. 

 Stomata wanting ; macrospores crested. 



Leaves stout, rigid, scarcely tapering. j. /. lacustris. 



Leaves slender, tapering. 2. /. l^ickermani. 



Stomata present ; macrospores echinate. 3. /. echinospora. 



Amphibious or submerged only in earlier stages ; stomata always present on the quad- 

 rangular leaves. 

 Peripheral bast-bundles wanting. 



Microspores papillose or tuberculate, not reticulate, white. 



Leaves 5-8 cm. long macrospores with minute warts. 4, 7. saccharata. 

 Leaves 10-20 cm. long : macrospores with jagged crests. 5. 7. riparia. 

 Microspores densely reticulate and often slightly papillose, dark brown ; macro- 

 spores with thick- walled reticulations. 6. I.foveolata. 

 Peripheral bast-bundles irregular or wanting ; submersed leaves very long ; macro- 

 spores with convolute labyrinthine ridges. 7. 7. Eatoni. 

 Peripheral bast-bundles present. 



Macrospores sparsely covered with irregular crests. 8. 7. Canadensis. 



Macrospores with honeycomb-like reticulations. 9. 7. Engelmanni. 



Terrestrial ; stomata abundant on the triangular leaves. 



Leaves 15-60, usually black at the base. 10. 7. melanopoda. 



Leaves 8-12, bright green, paler at the base. n. 7. Butleri. 



X. Isoetes lacustris L. (I. F. f. 102.) Submerged or rarely above water; 

 leaves 10-25, rigid, rather thick, scarcely tapering, dark or olive green, obtusely 

 quadrangular, 5-15 cm. long ; stomata none ; peripheral bast-bundles wanting ; 

 sporange orbicular or broadly elliptic, unspotted ; velum rather narrow ; ligule 

 triangular, short or somewhat elongated ; macrospores 50x5-800 // in diameter, 

 marked all over with distinct or somewhat confluent crests, and bearing three con- 



