GENTIAN FAMILY 



329 



a minute, slender, glabrous plant, 2 — 4 in. high, but little 

 branched ; leaves subulate, soon withering ; flowers yellow, only 

 expanding in bright sunshine. — Sandy heaths in the south, where 

 water has stood during the winter; rare. — Fl. July — October. 

 Annual. 



2. Blackstonia (Yellow-wort). — Erect, glaucous plants, with 

 perfoliate leaves ; flowers in loose dichasial cymes, yellow, 6 — 8- 

 metous ; calyx deeply lobed ; corolla 



rotate ; ovary 1 -chambered, many 

 ovuled ; style not persistent ; stigma 

 2 — 4-cleft. (Named in honour of John 

 Blackstone, an English botanist of the 

 1 8th century.) 



1. B. ferfolidta (Perfoliate Yellow- 

 wort). — The only British species, an 

 erect plant, 12 — 18 in. high, remark- 

 able for its glaucous hue, and for its 

 pairs of leaves, which are rather distant, 

 and are united at the base (connate) 

 with the stem passing through them, 

 whence the name Perfoliate. The 

 flowers, which are large and handsome, 

 are yellow, and expand only between 9 

 o'clock in the morning and 4 p.m. — 

 Chalk and limestone pastures ; not 

 uncommon. Fl. June — September. 

 Annual. 



3. Centaltrion (Centaury). — Erect, 

 herbaceous plants with angular stems ; 

 leaves sometimes united at the base ; 

 flowers in terminal, trichasial cymes; 

 corolla funnel-shaped, usually 5-lobed, 

 pink, white, or yellow ; stamens 4 — 5 ; 

 anthers becoming spirally twisted; style 

 simple, not persistent ; stigmas 2. — 

 (Name, like Centaurea, referring to the Centaur Chiron, who in 

 Greek mythology was famous for his medical skill.) 



1. C. umbelldtum (Common Centaury). — A pretty plant, 2 — 18 in. 

 high, with square, erect, green stems, much branched above ; 

 leaves elliptic-oblong, with strong parallel ribs, and remarkably 

 smooth ; flowers in terminal, corymbose, trichasial cymes, rose- 

 pink, or rarely white, only opening in fine weather ; calyx half as 

 long as corolla-tube ; filaments springing from the top of the 



blackst6nia perfoliXta 

 {Perfoliate Yellow-wort'). 



