STANDLEY TEEES AND SHRUBS OF MEXICO. 1233 



6. HELIOTROPIITM L. Sp. PI. 130. 1753. 



Shrubs or herbs; leaves alternate or opposite, entire; flowers small, In 

 secund spikes or in bifid cymes, sometimes axillary ; calyx 5-parted or 5-lobate, 

 the lobes usually narrow ; corolla salverform, the lobes broad or narrow ; style 

 short or elongate, the stigma conic or elongate ; fruit dry, 2 or 4-lobate, separat- 

 ing into 2 or 4 nutlets. 



Numerous herbaceous species occur in Mexico. 



Flowers subtended by bracts or leaves, never in forked spikes. 



Fowers few, crowded at the ends of the branches 1. H. confertifolium. 



Flowers numerous, mostly in secund spikes. 



Leaves narrowly linear, 1.5 mm. wide or less 2. H. angustifoliuna. 



Leaves linear or broader, 2.5 to 10 mm. wide. 



Fruit glabrous 3. H. rugosum. 



Fruit strigose. 



Pubescence of the stems chielly of reflexed hairs 4. H. mexicanum. 



Pubescence of the stems of erect hairs 5, H. fruticosum. 



Flowers in ebracteate spikes, these usually forked and forming cymes. 



Fruit at maturity separating into 2 2-celled nutlets 6. H. parviiloriim. 



Fruit separating into 4 1-celled nutlets. 

 Stems hirsute with spreading hairs, the pubescence fulvous. 



7. H. .ialisC'Snse. 

 Stems strigose or pilose with ascending hairs, the pubescence white or 

 gray. 

 Hairs on the lower surface of the leaves loose, not closely appressed. 



8. H. coriaceum. 

 Hairs on the lower surface of the leaves very closely appressed. 



Leaves linear, strongly revolute 9. H. pueblense. 



Leaves lanceolate or linear-lanceolate, not revolute-_10. H. calcicola. 



1. Heliotropium confertifolium Torr. ; A. Gray, Syn. Fl. 2': 1S4. 1874. 

 Heliotropium limhatum confertifolium Torr. U. S. & Mex. Bound. Bot. 138. 



1859. 



Coahuila, Nuevo Leon, and San Luis Potosi. Western Texas ; t3rpe from 

 Leon Springs. 



Plants sulTrutescent, 30 cm. high or less, much branched, densely whitish- 

 sericeous ; leaves linear or narrowly oblong, 4 to 8 mm. long, crowded and 

 imbricate; corolla pale purple, the tube about equaling the calyx. 



2. Heliotropium angustifolium Torr. U. S. & Mex. Bound. Bot. 137. 1859. 

 Coahuila to Tamaulipas and San Luis Potosi. Western Texas. 



Plants fruticose or suffrutescent, slender, 30 cm. high or less, canescent- 

 strigose ; leaves 8 to 20 mm. long, spreading, sessile ; corolla scarcely exceeding 

 the calyx, the lobes acute. 



3. Heliotropium rugosum Mart. & Gal. Bull. Acad. Brux. 112; 336. 1844. 

 Type from plains of Ejutla, Oaxaca. 



Plants fruticose, pilose ; leaves lanceolate, petiolate, 3.5 cm. long attenuate 

 at each end, rugose above ; corolla scarcely exceeding the calyx. 



4. Heliotropium. mexicanum Greenm. Proc. Amer. Acad. 33: 484. 1898. 

 Chihuahua and Durango to Oaxaca and San Luis Potosi; type from 



Guanajuato. 



Plants suffrutescent, 60 cm. high or less ; leaves oblong-linear to linear- 

 lanceolate, 1 to 5 cm. long, subsessile, strigose and hirtellous; corolla white, 

 5 to 6 mm. long. 



