THALAMIFLOR.E 99 



above, pollen must drop on its receptive surface as a 

 rule, leading to self-pollination. 



The siliqua opens upwards along both sutures 

 when ripe, and the seeds attached to the central 

 septum along the replum may be thrown to a dis- 

 tance when it contracts, or be blown away in a high 

 wind, the slight wing above assisting in this opera- 

 tion. 



The first Latin name is from the Greek eruo, draw 

 blisters. The name Treacle is derived from theriakel, 

 diminutive of therith, a little beast, the plant being, 

 along with vipers, an ingredient in Venice treacle, or 

 " Viper-wine." As the alternative English name 

 implies, the plant was used as a vermifuge. 



This plant is also called Treacle Mustard, Tarrify, 

 Treacle Wormseed, Worm-seed. 



Erysimum cheiranthoides. — In Fig. 12 note the 

 lanceolate, alternate leaves, the long flower-stalks, and 

 spreading siliquas, which are long and linear. 



White Mustard {Brassica alba). 



When found by the sea coast or by river-banks or 

 the way-side, the different species of Brassica may be 

 native, as the Sea Cabbage. The rest of them are 

 more or less all colonists. 



White Mustard is general in the British Isles, 

 south of Ross, in Scotland, but is rare in Ireland. 

 It is found also in the Channel Islands. It is one of 

 the ingredients of mustard and cress, and so may 

 often be an escape. 



