xxxiv 



53a. Leaves deeply pinnatifid; swamp plants with flowers in spikes 

 or solitary HALORAGIDACEAE, p. 79. 



53b. Leaves lobed, or irregularly pinnately cut or dissected; weedy 

 plants with flowers in racemes 2, in C03IPOSITAE^ p. 114. 



54a. Juice milky 3, in EUPHORBIACEAE, p. 67. 



54b. Juice not milky or colored 55. 



55a. Leaves whorled 56. 

 55b. Leaves all opposite 58. 



56a. Aquatic or mud plants with erect stems 



2a, in HALORAGIDACEAE, p. 79. 



56b. Prostrate weedy terrestrial plants AIZOACEAE, p. 31. 



56c. Erect or ascending terrestrial plants 57. 



57a. Leaves more than 2.5 cm. long 4a, in CORNACEAE, p. 83. 



57b. Leaves 2 cm. long or less 3a, in PRIMULACEAE, p. 87. 



58a. Flowers in terminal or axillary spikes, racemes, or other 



clusters 59. 

 58b. Flowers solitary or few in the axils of the leaves 61. 



59a. Leaves less than 5 mm. long la, in GENTIANACEAE, p. 88. 

 59b. Leaves more than 2 cm. long 60. 



60a. Inflorescence chiefly terminal, panicled 



2, in COMPOSITAE, p. 114. 

 60b. Inflorescence chiefly axillary URTICACEAE, p. 23. 



61a. Flowers on long pedicels 2, in CARYOPHYLLACEAE, p. 31. 

 61b. Flowers on short pedicels or sessile 62. 



62a. Stem erect, repeatedly branched; leaves linear to oblong 



ILLECEBRACEAE, p. 31. 

 62b. Stem decumbent or prostrate 63. 



63a. Leaves round, ovate, or kidney-shape, rounded at the base, cren- 

 ate or lobed 12a, in SAXIFRAGACEAE, p. 50. 



63b. Leaves of a narrower shape, entire, tapering toward the base 

 64. 



64a. Principal leaves 23 cm. long la, in ONAGRACEAE, p. 78. 

 64b. Principal leaves 1 cm. long or less 65. 



65a. Petals present ELATINACEAE, p. 74. 



65b. Petals none CALLITRICHACEAE, p. 68. 



66 



66a. Plants of the composite type, with several or many small 

 flowerets closely aggregated into a dense head surrounded or 

 subtended by a calyx-like involucre of small bracts 67. 



66b. Flowers solitary or variously clustered, but not in in- 

 volucred heads 70. 



