38 



ISOETACEAE 



7. Isoetes nuttallii A. Br. 



Nuttall's Ouilhvort. 



Fig. 79. 



Isoetes nuttallii A. Br.; Engelm. in Am. Nat. 8: 215. 1874. 

 Isoetes suksdorfii Baker, Handb. Fern Allies 132. 1887. 



Terrestrial in damp places ; corm slightly 3-lobed ; leaves 12-60, 

 light green, 3-angled, very slender, firm, erect, 8-17 cm. long; 

 stomata numerous ; peripheral strands usually 3, sometimes 2, lack- 

 ing dorsal one; ligule small, triangular; sporangia oblong, 4-7 mm. 

 long, completely covered by velum; megaspores white, chiefly 400- 

 528 H, rarely smooth, generally densely covered by small, often 

 glistening, distinct papillae on faces between prominent commis- 

 sural ridges; microspores brown, 25-30 [i long, papillose. 



Wet, springy places, Transition Zone; Oregon, Washington. California. 

 Type locality: "on damp flats and springy declivities, Columbia River." 



8. Isoetes orcuttii A. A. Eaton. Orcutt's Quillwort. Fig. 80. 



Isvctes orcuttii A. A. Eaton, Fern Bull. 8: 13. 1900. 

 Isoetes nuttallii orcuttii Clute, Fern Allies 253. 1905. 



Terrestrial ; corm slightly 3-lobed ; leaves 6-14, fine, erect, triangular, 

 2-8 cm. long; stomata present; peripheral strands none, or two weakly 

 developed; ligule triangular; sporangia orbicular to slightly elongated, 

 2-5 mm. long, completely covered by velum ; megaspores gray at 

 maturity, brownish when wet, 216-360 ^l, rarely 480 \.i, in diameter, 

 closely marked with numerous small indistinct papillae or almost 

 smooth, glistening; microspores 21-27 [i in length, chiefly spinulose. 



California, centra! and southern. Transition and Upper Sonoran Zones. Type 

 locality: "mesas in low depressions, San Diego." 



Family 6. EQUISETACEAE. 



Horsetail Family. 

 Rush-like plants, mainly of low situations, the rhizomes perennial, blackish, wide- 

 creeping, freely brancheci, rooting at the nodes. Aerial stems perennial or annual, 

 usually erect, cylindrical, fluted, simple or with whorled branches at the solid 

 sheathed nodes, the internodes usually hollow ; surfaces overlaid with silica in the 

 form of tubercles, cross-bands, rosettes, or a smooth covering ; stomata arranged 

 in broad bands or regular rows in the grooves. Leaves nodal, minute, united 

 lengthwise to form cylindrical or loose dilated sheaths, their tips (teeth) cpnnivent 

 or free, persistent or deciduous. Strobiles (spikes) terminal, formed of stalked 

 peltate bracts (sporophylls) arranged in close-set circles about a common axis, 

 these bearing a few sporangia beneath; spores uniform, green, provided with 

 4 hygroscopic bands. Prothallia minute, monoecious or dioecious, green, lobed. 



The family consists of the followring genus: 



1. EQUISETUM L. Sp. PI. 1061. 1753. 



Character of the family. [Name ancient, signifying horse-tail, in allusion to the copi- 

 ous bushy branching of many species.] 



About 25 species, mostly of very wide distribution. Type species, Equisctum fluiiatile L. 

 Spikes blunt or barely acute; aerial stems annual, not surviving the winter. 



Aerial .stems dimorphous, the fertile ones white, flesh-colored, or brownish, nearly devoid of chlorophyll, 

 the sterile ones green, much branched. 

 Fertile stems 5-25 cm. long, the sheaths with 8-12 teeth; spike 2-3 cm. long; sterile stems 10-60 cm. 



long, 6-14-furrowed, the branches 3- or 4-angled. 1- £• ar-^ense. 



Fertile stems 25-60 cm. long, the sheaths with 20-30 teeth; spikes 4-8 cm. long; sterile stems 0.5-3 

 meters long, 20-40-furrowed, the branches 4-6-angled. 2. E. tehnateia. 



Aerial stems uniform, green. j , ,, » 



Fertile stems mostly with numerous elongate verticillate branches; plants of swamps and shallow water. 



