or less covered by a velum; the microspores germinate into prothallia that bear 

 only a solitary antheridium; the megaspores germinate into prothallia that bear 

 only archegonia. 



This family is represented by two genera, Isoetes and Stylites. 



1. Isoetes L. Quillwort 



Characters same as those of the family. About 75 species that are wide- 

 spread in temperate and tropical regions of both hemispheres. 



A compound microscope is usually necessary in order to determine species. 



It has been noted that ducks seek out and eat the cormlike rhizomes and 

 sporangia masses at the base of the plant, and muskrats are known to eat the 

 crisp rhizomes. Wildfowl and grazing animals are also known to eat the grasslike 

 sporophylls. 



1. Velum complete; megaspores dark-brown when wet, small-tuberculate; leaves 

 12 cm. long or less; plants light-brown at base 1. /. lithophylla. 



1. Velum narrow, usually covering not more than one third of sporangium (2) 



2(1). Megaspores with tubercles frequently confluent into wrinkles; distribution 

 Arizona 2. /. Bolanderi. 



2. Megaspores with chiefly simple tubercles; distribution Oklahoma and Texas (3) 



3(2). Megaspores less than 480 microns in diameter; sporangia 5-30 mm. long, 

 brown-spotted, with narrow to broad velum 3. /. melanopoda. 



3. Megaspores more than 480 microns in diameter; sporangia 6-7 mm. long, 



usually brown-lineolate, the velum wanting or very narrow. 



4. /. Butleri. 



1. Isoetes lithophylla Pfeifi'er. Fig. 5. 



Corm 2-lobed, small; leaves 6 to 14, 10-12 cm. long, slender but not filiform, 

 flexuous; stomata numerous; peripheral strands variable, none or 3, weak; ligule 

 very small, cordate-triangular; sporangium 2.5-4 mm. long, orbicular to oblong, 

 completely covered by velum; megaspores 290-360 microns in diameter, with 

 prominent high rather narrow commissural ridges; surface of megaspores gray 

 when dry, brown when wet, smooth or faintly marked with low short or somewhat 

 extended usually distant ridges; microspores dark brown, chiefly 30-33 microns 

 long, high-tuberculate or spiny. 



In shallow depressions and temporary pools on rock outcrops and mts. of 

 granite, found only in Burnet and Llano cos. on the Edwards Plateau in Tex. 

 where it is apparently endemic, Apr.-June. 



2. Isoetes Bolanderi Engelm. Fig. 7. 



Corm usually conspicuously 2-lobed; leaves 6 to 25, conspicuously quill-like, 

 6-15 cm. long, rarely more; stomata very few; ligule small, cordate; sporangium 

 3-4 mm. long, orbicular to oblong, at most one-third covered by velum; mega- 

 spores white to bluish, 300-480 microns in diameter, the tubercles sometimes 

 aggregated into wrinkles; microspores 23-30 microns long, more or less spinulose. 



Submersed in bottom of lakes and ponds in shallow to deep water, rare in 

 Ariz. (Apache and Coconino cos.); B.C. s. to Mex. 



Plants small in all characters have been recognized as var. pygmaea (Engelm.) 

 Clute. Calif., Nev. and Ariz. 



3. Isoetes melanopoda Gay &. Dur. Fig. 5. 



Corm 2-lobed; leaves 15 to 60, slender, erect, firm, bright green, 15-40 cm. 

 long, usually black and shining at base, with usually pale membranaceous border, 

 little (2-3 cm.) extended above sporangium level; stomata present; peripheral 

 strands 4 or 6 cardinal, plus as many as 14 accessory groups; ligule subulate- 

 triangular; sporangia oblong, 5-30 mm. long, marked by numerous brown spots; 



43 



