style lobed or entire, seated in the pericarp at the apex of the fruit or borne between 

 the fruit lobes (nutlets) on the receptacle, or on an upward prolongation thereof 

 (gynobase) ; endosperm absent or scarce. 



The classification of this large family is based primarily upon the structure of 

 the fruit. In many cases it is very difficult to recognize the genus and almost impos- 

 sible to obtain a precise identification of the species if the specimens lack mature 

 fruiting structures. Numerous species are cultivated as ornamentals, notably in the 

 genera Heliotropium (heliotrope), Anchusa, Echium and Myosotis (forget-me-not). 



1. Ovary entire or shallowly lobed, the style terminal 1. Heliotropium 



1. Ovary deeply 4-lobed, the style borne on the gynobase and arising between 



the lobes of the ovary (2) 



2(1). Mericarps conspicuously armed with glochidiate prickles 2. Hackelia 



2. Mericarps smooth and shining or rugose, lacking glochidiate prickles (3) 



3(2). Leaves typically narrowly oblanceolate to spatulate; mericarps basally 

 attached to a flat gynobase, smooth and shining; corolla lobes 

 convolute in bud 3. Myosotis 



3. Leaves typically ovate to lanceolate; mericarps obliquely attached to a convex 



gynobase, rugose and not shining; corolla lobes imbricate in bud 

 4. Mertensia 



1. Heliotropium L. Turnsole. Heliotrope 



Annual or perennial, herbaceous or more or less shrubby plants; leaves small to 

 large, sessile or petiolate; cymes unilateral and generally distinctly scorpioid, with 

 or without bracts; corolla white, yellow or purple, variable in form, throat fre- 

 quently pubescent inside; anthers included, filaments extremely short; style present 

 or absent; stigma usually frustrumlike or conic, mostly sterile, receptive only in a 

 band around the base; fruit dry, at maturity breaking up into 4 1 -seeded or 2 

 2-seeded mericarps; seeds usually with a thin endosperm. 



About 250 species widely represented in the warmer parts of the world. The 

 species are particularly numerous in arid regions. 



L Mature fruit breaking up to form 2 2-seeded mericarps; leaves evidently 

 veined; cymes bractless (2) . 



1. Mature fruit breaking up into 4 1-seeded mericarps; leaves may or may not 



be evidently veined; cymes with or without bracts (3) 



2(1). Plant with simple hairs; leaf blades ovate to broadly lanceolate or some- 

 what cordate, 3-6 cm. long, 1-4 cm. wide; veins numerous, evident, 

 branched; fruit with a corky mesocarp; each mericarp with a single 

 sterile cell 1. H. molle. 



2. Plant with malpighiaceous hairs on stems and leaves; leaf blades lanceolate, 



2-4.5 cm. long, rarely* more than 1 cm. wide; veins few or none, 

 obscure, always simple; fruit lacking a corky mesocarp; each meri- 

 carp with 3 sterile cells of which the 2 larger are partially filled 

 with corky tissue 2. H. glabriusculum. 



3(1). Plant very succulent, glabrous, usually somewhat glaucous (4) 



3. Plant not noticeably succulent, hairy, never glaucous (6) 



4(3). Corolla white, the limb 1.5-3 mm. in diameter; leaves 8 mm. wide or less 

 3. H. curassavicum var. curassavicum. 



4. Corolla white and often purple-tinged at throat, the limb more than 3 mm. 



in diameter; leaves to 2 cm. wide (5) 



5(4). Corolla limb 3-5 mm. in diameter 3. H. curassavicum var. oculatum. 



5. Corolla limb 5-10 mm. in diameter 3. H. curassavicum var. obovatum. 



1384 



