108 CALIFORNIA ACADEMY OF SCIENCES. 



3. C. SERPYLLiFOLius, Nutt. Gen. i. 154; Watson, I. c. 

 335. — Georgia. The localit}^ in Nuttall's Genera, and on 

 an original specimen in the Gray herbarium, is Florida. 



* ^ Flowers white: inflorescence rather simple and 



mostly compact, at the ends of slender usually 

 leafless or nearly leafless peduncles: twigs subte- 

 rete, not spinose : leaves ample or medium-sized (15 

 to 75 mm. long), thin, toothed, 3 -nerved: fruit 

 about 4 mm. in diameter. — Atlantic or Rocky 

 Mountain species. 



4. C. Americanus, L. Spec. 195; Watson, I. c. 333, In- 

 dex, 163. — Ontario to Manitoba, south to Florida and Tex- 

 as. 



5. C. ovATus, Desf. Arb. ii. 381; Watson, I. c. 334.— Can- 

 ada and the lake region to Texas. 



VAR. PUBESCENS, Watson, Index, 166. — Rocky Mount- 

 ain region. 



* * ^ Flowers blue: inflorescence compound, ample, on 



leafy branches : twigs conspicuously sulcate : leaves 

 medium-sized (25 to 50 mm. long), prominently 3- 

 ribbed, minutely glandular-serrulate: fruit mostly 

 5 or 3 mm. in diameter. 



6. C. THYRSIFLORUS, Esch. Mem. St. Petersb. Acad. x. 

 285; Watson, I. c. 334. — Mountains of Western Califor- 

 nia. 



* * * * Flowers blue (often pale) or white: inflorescence 

 compound, rather loose, on few-leaved branches: 

 leaves entire, mostl}' medium-sized. — Pacific spe- 

 cies. 



-i- Twigs (more or less spinose in the first) usually 

 somewhat angled and often twisted: leaves rather 

 firm or even coriaceous. 



