BRITISH FLOWERING PLANTS 



34 



containing the seeds. Several species yield a 

 strong essential oil. We have only space to 

 notice one or two plants belonging to this extensive 

 Order in detail. 



White Mustard — Sinapis alba 

 (Plate X) 



Mustard is a troublesome weed in arable land, 

 and all the more so because it harbours various 

 insects which are very injurious to cultivated crops, 

 especially the dreaded " Turnip Fly." This is a 

 collective name for several small species of shining 

 metallic greenish or bronzy beetles, with or without 

 yellow markings, which have thickened hindlegs 

 and skip about like fleas. They belong to the 

 genus Haltica and its allies. 



The flowers of the White Mustard are yellow, 

 and the flower-stalks are angular, and stand erect 

 when they bear the pods. The pods are very 

 pilose, and are furnished with a long sword-shaped 

 beak. The seeds are white or brown, and number 

 from 3 to 5 in a pod. This plant is some- 



times cultivated, and mustard is prepared from 

 the ground seeds. It is in daily use as a con- 

 diment ; and is of great value as a household 

 medicine, either mixed with water as an emetic, 

 or as a poultice for chest complaints. 



Woad — I satis tinctoria 

 (Plate XI) 



This plant is largely cultivated in many parts of 

 the Continent, especially in Eastern Germany and 

 Austria, for the preparation of indigo from the 

 root. It is so scarce and local in England that 

 botanists have doubted whether it is truly in- 

 digenous, although it is with the juice of this 

 plant that the Britons are said to have stained 

 their bodies blue in the time of Caesar. 



The root is turnip-like and biennial, and the 

 plant flowers in the second year. The root-leaves 

 are oval, smooth, narrower at the base, and 

 notched on the borders. The stem grows to the 

 height of 2 or 3 feet, and is enclosed by the leaves. 

 The stem divides into several branches, which 



