26 JIEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 



KEY TO THE SPECIES. 



Outer segments of calyx unchanged or developing keels in fruit. 



Inflorescence consisting mostly of axillary and terminal clusters and simple 



racemes ; achene granular. 

 Inflorescence consisting mostly of axillary and terminal panicled racemes; 



achene smooth. 

 Outer segments of calyx developing conspicuous wings. 



Inflorescence consisting of axillary and terminal simple racemes. 



Racemes leafy ; fruiting calyx 1 cm. long ; wings crisped. 



Racemes leafy -bracted ; fruiting calj^x .5 em. long ; wings nearly flat. 



Racemes naked; fruiting calyx .5 cm. long; wings incised. 

 Inflorescence consisting of axillary and terminal pauicled racemes. 



g. SUBGENUS ECHINOCAULON. 



Herbaceous plants, glabrous but usually armed, annual or sometimes perennial. 

 Stem ascending and reclining, four-angled, more or less channeled, armed on the angles 

 Avith recurved prickles, by means of which it climbs over objects. Leaves truncate, has- 

 tate or cordate, membranous, petioled or sessile, the petiole, midrib and principal nerves 

 armed with small recurved prickles. Ocreae funnelform, very oblique, finely nerved, 

 variously roughened about the base. Inflorescence terminal and axillary, more or less 

 paniculate or dichotomous, the ultimate divisions ending in spicate racemes, usually 

 somewhat interrupted or capitate clusters. Calyx somewhat colored, four-parted or five- 

 parted. Stamens varying from five to eight, mostly in fives, sixes or eights, included. 

 Style two-cleft or three-cleft, mostly two-parted or three-parted, included. Achene lenti- 

 cular or triquetrous, variously colored, strongly biconvex or sharply angled, smooth and 

 shining. Albumen horny. Cotyledons accumbent. 



KEY TO THE SPECIES. 



Leaves sagittate or subsagittate ; achene triquetrous. 



Inflorescence dichotomous ; leaves subsagittate, nearly sessile. 68. P. Meisnerianum. 



Inflorescence simple or paniculate; leaves sagittate, more or less petioled. 69. P. sagittatum. 



Leaves hastate; achene lenticular. TO. P. arifolium. 



