FLOWERING PLANTS AND FERNS OF ARIZONA 699 



5. Stigmas 2, more or less elongate (6). 



6. Style entire; stigmas ovate or oblong; stems not or scarcely twining. 



5. Jacquemontia. 



6. Style 2-cleft at apex, or entire; stigmas linear-filiform to ovate; 



stems mostly twining 6. Convolvulus. 



1. CUSCUTA" Dodder 

 Contributed by T. G. Yuxcker 



Plants leafless and rootless, herbaceous, parasitic; stems yellowish, 

 filiform, twining; flowers small (mostly 2 to 6 mm. long), sessile or 

 short-pedicellate, in few- to many -flowered cymose clusters, commonly 

 5-merous but regularly 3- or 4-merous in a few species; perianth parts 

 mostly united ; stamens inserted in the throat of the corolla, alternating 

 with the lobes; appendages commonly present at base of the corolla 

 opposite the stamens, these scalelike, more or less toothed, fringed, or 

 fimbriate; ovary 2-celled, the styles 2, the stigmas (in the Arizona 

 species) capitate ; fruit a capsule, this remaining closed, or opening with 

 a regular or irregular line of circumscission near the base; embryo 

 acotyledonous, filiform or more or less enlarged at one end. 



Upon emergence from the seed the slender, elongate seedling coils 

 about an available host to which it becomes firmly attached by means 

 of its suckerlike organs (haustoria). A few species have been shown 

 to possess small amounts of chlorophyll and are thereby partly auto- 

 phytie. Although certain dodders show a preference in the choice of 

 host, most of them grow readily upon various plants. Those which 

 parasitize economically important crops sometimes cause considerable 

 damage. This is especially true in fields of clover and alfalfa, where 

 dodder seeds are commonly introduced with those of the host. 



Key to the species 



1. Capsules not circumscissile, i. e., not separating in a regular line of cleavage, 

 when forcibly separated either coming away entirely from the receptacle 

 or breaking very irregularly (2). 

 2. Flowers mostly 3- or 4-parted (3). 



3. Perianth membranaceous, the lobes obtuse; corolla lobes not inflexed at 

 tip; scales oblong, reaching the filaments and free from the corolla 

 tube above; corolla when withered remaining at top of the capsule. 



1. C. CEPHALAXTHI. 



3. Perianth fleshy-papillate, the lobes acute; corolla lobes erect with inflexed 



tips; scales reduced to lateral wings along the stamen attachment. 



5. C. CORYLI. 

 2. Flowers mostly 5-parted (4). 



4. Infra>tamineal scales lacking; perianth part-^ acute to acuminate; calyx- 



lobes triangular-ovate to sublanceolace; corolla lobes lanceolate, 



reflexed 3. C. califorxica. 



4. Infrastamineal scales present (5). 



5. Perianth fleshy-papillate; corolla lobes commonly erect, with inflexed 

 tips; scales prominent and mostly free from the corolla tube, at least 



above 4. C. ixdecora. 



."J. Perianth not fleshy-papillate; corolla lobes various, but not as in C. 

 indecora (6). 



6. Corolla lobes triangular or lanceolate, acute to acuminate (7). 



7. Scales free from the corolla tube only at the upper end, included; 



perianth lobes lanceolate, acute to acuminate: capsules globose- 

 conic, mostly 1-seeded (i. C. SALINA. 



References: Yuncker, T. G. revision- of the north American and west imman species of crs- 

 o-ta. Univ. 111. Biol. Monog. 6: 1-142. 1921. 

 the genus ci-scuta. Torrey Bot. Club Mom. IS: 1 13-331, 



