102 American Midland Naturalist Monograph No. 7 



5. Leaves in whorls of four, linear-oblanceolate; wings acumi- 

 nate; sandy soil in the northern half of the state. July- 

 Sept P. cruciata L 



4. Racemes slender, cylindrical or linear, tapering, less than 5 mm 

 thick. 



7. Branches mostly opposite or whorled; racemes short- 

 pedvmcled; flowers green or greenish; dry soil, locally 

 throughout 111. July-Sept P. verticillata L. 



7. Branches mostly alternate; racemes long-peduncled; flowers 

 purplish or greenish-purple; woods and fields; extending 

 northward to Cass and Cumberland counties. June-Aug. 

 P. arnbigua Nutt 



43. Euphorbiaceae J. St. Hil. — Spurge Family 



1. Flowers not in an involucre; calyx of 3-5 sepals; sap water>'. 

 2. Pubescence of stellate hairs. 



3. Flowers in spikes or glomerules; ovary 3- (2-4-) loculed 1. Croton 



3. Flowers scattered on the branchlets; ovary 1 -loculed 2. Crotonopsis 



2. Pubescence, if any, of simple hairs. 



4. Leaves entire; stamens usually 3; styles simple; bracts of the pistillate 



flowers not cleft 3. Phyllanthus 



4. Leaves serrate. 



5. Bracts of the pistillate flowers cleft; styles many-cleft; stamens 



usually 8; stems not twining 4. Acalypha 



5. Bracts not cleft; styles 3; stamens 1-5; stem (in our species) 



twining, and the leaves ovate-cordate, dentate 5. Tragia 



1. Flowers in a cup-shaped calyx-like involucre; sepals rudimentary; sap 

 milky. 



6. Leaves opposite, oblique at base 6. Chamaesyce 



6. Leaves not oblique at base, alternate or opposite. 



7. Inflorescences in a several-rayed umbel; stipules none 7. Euphorbia 



1 . Inflorescences cymose; stipules gland-like 8. Poinsettia 



1. Croton L. 



1. Leaves serrate; staminate flowers with a 4-parted calyx, 4 petals, 

 a 4-rayed disk, and 8 stamens; pistillate flowers with a 5-parted 

 calyx; styles 3, bifid; sandy soil; adv. from southern U.S. 

 Aug. -Oct. Sand Croton C. glandulosus L. 



L Leaves entire. 



2. Capsules clustered, erect, depressed-globose, 7-9 mm in diam- 

 eter; styles 3, bifid or trifid; stamens 10-14; sandy soil; 



absent from the extreme northern counties. Aug.-Sept 



C. capitatus Michx. 



2. Capsules mostly solitary, pendent, ovoid, 3-4 mm long; style 

 none, the stigmas 2, bifid; stamens 3-8; roadsides and fields; 

 chiefly in the southern half of 111. ; also Cook Co. July-Oct. 

 C monanthogynus Michx. 



