GENUS 16. 



SPURGE FAMILY. 



471 



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



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

 topped by several-rayed umbel-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 peduncled, axillary, 

 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 exserted, 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 species: Euphorbia dcndroidcs 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. 



2. T.obtusatits. 



Glands sessile ; warts on the capsules depressed ; seeds smooth. 3. T. platyphyllus. 



Seeds strongly and prominently reticulated. 

 Glands nearly sessile ; capsules warty. 



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

 or broader. 4. T. tnissonricnsis. 



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



5. T. arkansanus. 

 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 ^"-i l A" 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. n. T.Peplus. 



Capsules with rounded lobes. 12. T, commutatus. 



Leaves thick, sessile. 13. T. robustus. 



6. T. Helioscopia. 



7. T.Esula. 



8. T. Incidus. 



9. T. Cyparissias. 

 10. T. Darlingtonii. 



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



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

 Tithymalus 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, 2.\"-$" 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. 



