104 POPULAR FIELD BOTANY. 
THLASPI PERFOLIATUM. Perfoliate Shepherd’s Purse. 
This species is rare, and indeed only seems to be found 
in Oxfordshire and Gloucestershire. The stem-leaves are 
heart-shaped, smooth, somewhat toothed and not stalked ; 
root-leaves stalked and egg-shaped. Flowers very small, 
white, and in a dense bunch. A smaller plant than the last. 
TETRADYNAMIA, SILIQUOSA. 
THALAMIFLORA. CRUCIFERZ. 
ARABIS. (Watt-Crzss.) 
Generic Character. Calyx of four oblong, erect leaves, two 
opposite ones somewhat larger, all falling off. Petals oblong, 
undivided, spreading, hardly as long as the calyx. <Anthers 
heart-shaped. Pod narrow, compressed, valves nearly flat, ribbed 
or veined, slightly undulated by the seeds. 
Arasis THattana. Common Wall-Cress. Stem about 
a foot high, branched. Leaves hairy and toothed, root- 
leaves stalked, oblong, the rest having no stalks. Flowers 
small, white, and in a bunch. This little plant is_ common 
in the spring on walls and loose sandy soil. 
Arasis stricta. Bristol Rock Cress. This is a rare 
species, found in rocky places about Bristol. It has cream- 
