Genus i6. 



SPURGE FAMILY. 



471 



16. TITHYMALUS [Tourn.] Adans. Fani. 2: 355. 1763. 



Annual or perennial herbs or shrubby plants, with simple or branched stems, which are 

 topped by several-rayed unibel-like cymes. Leaves below the umbel usually scattered or 

 alternate, without stipules, often broadened upward. Bracts of the umbel quite different 

 from the stem-leaves ; blades entire or toothed. Involucres sessile or pcduncled, a.xillary, 

 disposed in open or close cymes; lobes often toothed. Glands 4, transversely oblong, reni- 

 form or crescent-shaped by the horn-like appendages, the missing one represented by a thin 

 often ciliate lobe. Capsule e.xserted, smooth or tuberculate; lobes rounded, sharp or keeled. 

 Seeds variously pitted, often with caruncles. [Greek, referring to the milky juice of these 

 plants.] 



About 250 species of wide geographic distribution. Besides the following, several others occur 

 in western North America. Type speciea: Euphorbia dendroides L. 



Leaves mainly opposite and decussate: capsules 5" wide or more. i. T. Lathyrus. 



Leaves alternate or scattered ; capsules less than 5" wide. 



Leaves serrulate ; glands of the involucre oblong, oval or orbicular. 

 Seeds smooth or faintly reticulated. 



Glands stalked ; warts on the capsules elongated ; seeds faintly reticulated. 



seeds smooth. 



6. T. 



Glands sessile ; warts on the capsules depressed 

 Seeds strongly and prominently reticulated. 

 Glands nearly sessile ; capsules warty. 



Upper stem-leaves with small basal lobes ; bracts of the umbel about as 



or broader. 4. T. 



Upper stem-leaves merely sessile; bracts of the umbel manifestly longer 



5. T. 

 Glands stalked ; capsules smooth. 

 Leaves entire ; glands of the involucres crescent-shaped or reniform. 

 Plants perennial ; seeds smooth. 

 Glands crescent-shaped, horned. 



Stem-leaves 2" 6" broad ; capsules smooth. 



Leaves subtending, the umbel lanceolate or oblanceolate. 

 Leaves subtending, the umbel ovate, oval or obovate. 

 Stem-leaves ;4"-i li" broad ; capsules granular on the lobes 

 Glands reniform, not horned. 

 Plants annual or biennial ; seeds pitted or rugose-pitted. 

 Leaves thin, petioled. 



Capsules with 2-crested lobes. 

 Capsules with rounded lobes. 

 Leaves thick, sessile. 



obtusatns. 

 flatyfhyllus. 



7. 



8. 



9- 



10. 



broad as long 

 tnissouricnsis. 

 than broad. 

 arkansanns, 

 Helioscopia. 



13- 



Esula. 

 liicidus. 

 Cyparissias. 

 Darlingtonii. 



Peplus. 



coinmutatus, 



robtistiis. 



I. Tithymalus Lathyrus (L.) Hill. Caper or Myrtle Spurge. Fig. 2753. 



Euphorbia Lathyrus L. Sp. PI. 457, 1753. 

 Tifhymalus Lathyrus Hill, Hort. Kew. 172/3. 1768. 



Annual or biennial, glabrous, stout, glaucous. 

 Stem usually erect, stout, 8-3 tall, mostly simple 

 below, umbellately branched above; leaves numer- 

 ous, the lower scattered, those subtending the 

 umbel verticillate, the lower linear, reflexed, the 

 upper lanceolate or linear-lanceolate, l'-5' long, 

 entire, sessile, subcordate at the base; bracts op- 

 posite, ovate or ovate-lanceolate, truncate or sub- 

 cordate; involucres 2i" long, bearing 4 crescent- 

 shaped unappendaged glands prolonged into short 

 horns ; capsule subglobose, 5"-6" in diameter, its 

 lobes rounded ; seeds oblong-ovoid, 2i"-3" long, 

 terete, usually wrinkled. 



In waste places, Connecticut to North Carolina. 

 Also in California. Native of Europe. Wild caper. 

 Caper-bush. Mole-tree or -plant. Spring-wort ; its 

 seeds a cathartic. May-Aug. 



