24 



MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 



Annual or perennial, but not by rootstocks. 

 Plants prostrate ; achenes exserted. 

 Leaves shorter than the internodes. 

 Leaves longer than the internodes. 

 Plants prostrate ; achenes included. 



Achene pointed at the apex, rounded at the base. 



Leaves mostly obtuse; style three-parted to the base. 

 Leaves mostly acute ; style three-parted to below the middle. 

 Achene pointed at both ends. 



Slender and wiry ; leaves narrow ; plants not arctic. 

 Short and stout ; leaves broad ; plants arctic. 

 Plants erect ; achenes conspicuously exserted. 

 Plants erect ; achenes included, never conspicuously exserted. 

 Flowers in axillary clusters. 



Branched throughout ; branches more or less spreading ; large plants. 

 Achene broadly ovoid ; style three-parted to below the middle. 

 Achene bi-oadly ovoid ; style three-parted to the base ; leaves 



mostly fugacious. 

 Achene ovoid ; style very short, three-parted to the base ; leaves 

 not fugacious. 



Branched mainly from the base ; branches erect or ascending ; 

 small plants. 

 Pedicels erect. 



Leaves oblanceqlate, sometimes much reduced above; 



achene narrowly oblong ; style nearly wanting. 

 Leaves obovate, not much reduced above ; achene oblong ; 



style three- parted. 

 Leaves linear or linear-lanceolate ; achene ovoid. 

 Pedicels deflexed. 

 Achene oblong. 



Achene ovoid, not constricted at the ends. 

 Achene ovoid; constricted at both ends. 

 Flowers in mostly interrupted spicate racemes at the ends of branches. 

 Achene oblong ; filaments not conspicuously dilated ; style three- 

 parted to the middle. 

 Achene ovoid ; filaments conspicuously dilated ; style three- 

 parted to base. 

 Flowers mostly in continuous terminal spicate racemes. 

 Racemes bracted. 



Outer calyx segments longer than the inner; bracts winged. 

 Outer calyx segments not longer than the inner; bracts not 

 winged. 

 Racemes leafy ; leaves hardly imbricated. 



42. P. EREOTUM. 

 45. p. CAMPORUM. 

 44. P. RAMOSISSIMTJM. 



52. P. spergulariaeporme. 



