Okdek 101.— marvelworts. 275 



COHORT III. 



THE APETALOUS EXOGENS. 



Essential Character, — Flowering plants (Pii^nogamia), 

 with their stems growing by additions to the outside and the 

 wood in circular layers (Exogens), with the seeds inclosed in 

 seed-vessels (Angiospeems), and the flowers destitute of petals 

 (Apetal^). 



Order C— ARISTOLOCHIACE^. Birthworts 



Low lierhs or climbing shrubs with alternate leaves^ \axgQ flowers ; 

 calyx adlicring to the ovary, valvate in bud, brown or dull colored ; 

 stamens 6-12, at top of the 6-celled, many-seeded ovary. 



Analysis of the Genera. 

 Ca]yx bell-form, rej^ular, 3-clcft. Stamens 12. Herbs with creeping, 



underground stems. . Wild Ginger. Asa'rcm, 1 



Calyx tubular, bent, irregular. Antbers 6. Shrubby, erect or climbing, 



with very odd flowers. Birthwort. Aristolo'chia. 



AS A RUM. "Wild Ginger. 



1 A Canadense. Canada W. Leaves in pairs, broad-rcniform, with the single flower 



between the petioles scarcely above-ground. May-July. c. 



2 A. Virginicum. Virginia W. Leaf solitary, round-ovate, cordate, the single flower 



much shorter than the petiole. Sepals obtuse. Mts. Va. S. April. 

 8 A. ariforium. Arum-lv. W. Leaf solitary, broadly hastate, wdth long, angular 

 lobes at base. Calyx throat contracted, lobes very short. Va. S. April. 



Order CI.— NYCTAGINACEJi]. Marvelworts. 



Her}>8 (shrubs or trees) with swelling joints; entire, opposite leaves ; 

 flowers surrounded by an involucre (which is, of course, calyx-like when 



the flower is solitary) : 

 calyx often colored like a corolla, tubular or funnel-form, breaking off 



above the Icolled, 1-secded ovary. 



