60 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



7. SELAGINEIXACEAE. Selag^inella Family. 



1. jSELAGINELLA Beauv. 



lieaves very numerous, alike, appressed, widely overlappicg, many-ranked, linear- 

 lanceolate, ending in a slender whitish awn 1. S. rupestris . 



Leaves few, of 2 kinds, 4-ranked, spreading in 2 planes, ovate, acute or cuspidate. 



2. S. apoda. 



1. Selaginella rupestris (L.) Spring. 



Exposed rocky bluffs; found only in vicinity of Great Falls, both sides of the river. 

 Ont. and eastern U. S. 



2. Selaginella apoda (L.) Fernald. 



Low moist situations, usually in partial shade; common. Me. to the Gulf Btates, 

 westward. {S. apus Spring.) 



8. ISOETACEAE. Quillwort Family. 



1. ISOETES L. Quillwort. 



Leaves 50-100, erect, 30-60 cm. long, with bast bundles 1. I. engelmannl valida. 



Leaves 10-30, spreading or recurved, 3-25 cm. long, without bast bundles. 



2. I. saccharata. 



1. Isoetes engelmannl valida Engelm. 



Temporary pools among rocks; Virginia shore of the Potomac, between Sandy Land- 

 ing and Great Falls; rare. N.J. toVa. 



2, Isoetes saccharata Engelm. 



Shallow water between tides, on gravel and sand ; banks of the Potomac at Fourmile 

 Run, Hunting Creek, and Mount Vernon; not uncommon. Mass. to Va. 

 Extremely variable, several forms having been described. 



9. PINACEAE. Pine Family. 



Leaves scalelike or awl-shaped, opposite 4, JUNIPEB.US . 



Leaves linear, needle-like. 

 Leaves in fascicles 1. PINITS. 



Leaves solitary. 

 Leaves stiff, about 10 mm. long, obtuse, persistent, dark green above, pale 



beneath; cones oblong, 2 cm. long or more, the scales rounded. ..2. TSUGA. 

 Leaves slender, about 15 mm. long, acute, deciduous, light green on both faces; 



cones globose or nearly so, the scales thick, woody 3. TAXODIirM. 



1. PmUS L. Pine. 



Leaves 5 in a fascicle; cones more than 9 cm. long, maturing the first year, the scales 



without bristles 1. P. strobus. 



Leaves 2 or 3 in a fascicle; cones less than 9 cm. long, maturing the second year, each 

 scale bearing a bristle near the apex. 

 Leaves 3 in a fascicle. 



Leaves 7-12 cm. long; cones ovoid, 3.5-7 cm. long 2. P. rigida. 



Leaves 15-24 cm. long; cones oblong, 7-12 cm. long 3. P. taeda. 



Leaves 2 in a fascicle. 



Leaves slender, about 1 mm. in diameter, 6 cm. long or more 4. P. ecliinata. 



Leaves stout, about 2 mm. in diameter and 4 cm. long. 



Cone scales tipped with a slender straight fragile prickle 5. P. virginiana. 



Cone scales tipped with a thick curved woody persistent prickle. 



6. P. pnngens. 



