CL. XV.] TETRADYNAMlA SILICULOSA. 265 



pressed. Style none; stigma obtuse. Pouch egg-shaped, trans- 

 versely compressed, entire, two-celled, two-valved; the valves 

 deeply concave; partition membranous, elliptical, parallel to the 

 valves, crossing the narrowest diameter of the pouch. Seeds egg- 

 shaped, four or more in each cell. Name, from subula, an 

 awl. 314. 



1. S. aqudtica. Water Awl-wort. Root of numerous white fibres: 

 leaves awl-shaped, spreading : flowers in a simple, stalked cluster, 

 arising from the root: petals white. Annual : flowers in July : grows in 

 shallow water, in sand or gravel, near the edges of Alpine lakes : fre- 

 quent. Eng. Bot. vol. xi. pi. 732. Eng. Fl. vol. iii. p. 157. 929. 



2. DRA'BA. WHITLOW-GRASS. 



Calyx of four, somewhat spreading, egg-shaped valves, equal at 

 the base. Petals spreading, with short claws. Filaments awl- 

 shaped; anthers two-lobed. Germen egg-shaped. Style very 

 short; stigma knobbed, flat. Pouch oblong, compressed, entire, 

 two-celled ; the valves nearly flat ; partition membranous. Seeds 

 several in each cell, small, roundish. Name, from drabe, 

 acrid. 315. 



1. D.vgrna. Common Whitlow-grass. Stem leafless; petals deeply 



cleft; leaves lance-shaped, toothed, hairy. Leaves arranged in a 



star-like form on the ground : flowers white, in a corymbose cluster. 

 Annual : flowers in March and April : grows on walls and dry loose soil : 

 common. Eng. Bot. vol. ix. pi. 586. Eng. FL vol. iii. p. 158. 930- 



2. D. aizoides. Yellow Alpine Whitlow-grass. Stem leafless ; petals 

 slightly notched, twice as long as the calyx ; leaves lance-shaped, stiff, 



glossy, fringed and keeled. Flowers of a bright-yellow colour : pouch 



with a long style. Perennial : flowers in March and April : grows on 

 walls and rocks about Swansea, Wales. Eng. Bot. vol. xviii. pi. 1271. 

 Eng. Fl. vol. iii. p. 158. 931. 



3. D.ruplstris. Hairy Whitlow-grass. Stem nearly leafless; petals 

 undivided ; leaves lance-shaped, slightly toothed, fringed with simple 



hairs. Stalk solitary, two or three inches high, round, leafless, or with 



a single leaf, near the bottom : flowers small, white, in a dense corymb, 

 Perennial : flowers in May and June : grows on high mountains in Scot- 

 land : rare. Eng. Bot. vol. xix. pi. 1338. D. hirta. Eng. Fl. vol. iii. 

 p. 159. 932. 



4. D. incdna. Twisted-podded Whitlow-grass. Stem-leaves numerous, 

 lance-shaped, hoary, like the stem, with starry hairs; pouch oblong, 



oblique or twisted, longer than the hairy flower-stalks. Stem from 



two to twelve inches high. Root-leaves arranged in a star-like form: 

 flowers numerous, white, with inversely heart-shaped petals. Biennial ; 

 flowers in May and June : grows in rocky places, on the mountains of 

 Scotland, Wales, and the north of England: frequent. Eng. Bot. vol. vi. 

 pi. 388. Eng. Fl. vol. iii. p. 160. 933. 



5. D. murfdis. Speedwell- leaved Whitlow-grass. Stem branched ; leaves 

 heart-shaped, toothed, hairy ; pouch elliptical, obtuse, flat, shorter than 



the partial stalks. Stem erect, about a foot high, leafy, rough with 



starry hairs : flowers very numerous, small, white. Annual: flowers in 



Z 2 



