CLASSIFICATION OF ANGIOSPERMS. 283 



b. CRUCIFER^ OR MUSTARD FAMILY.— These are 

 herbaceous plants with characteristic flowers and fruits. The 

 flowers have four sepals in two sets,. four petals which are more or 

 less spreading and clawed at the base, and six stamens which are 

 tetradynamous (Fig. 134, B). The fruit is a 2-celled silique or 

 silicle, which varies in shape in the different genera (Fig. 89). 



Sinapis alba (white mustard). — The plant is a slender, branch- 

 ing, more or less hispid (bristly hairy) annual or biennial herb 

 usually less than 0.5 M. high, with deeply pinnatifid lower leaves 

 and lanceolate, dentate upper leaves. The flowers are yellow, and 

 the silique is densely hispid, constricted between the seeds and 

 terminated by a long, flat, sword-like beak. The seeds are official 

 as white mustard (p. 428) but are known in commerce as yellow 

 mustard. 



Brassica nigra or black mustard, the seeds of "which constitute 

 the official black mustard (p. 429), is a larger, more branching 

 plant than Sinapis alba, being from i to 3 M. high. The silique 

 is shorter, more cylindrical and with a slender, filiform beak. 



Glucosides similar to those which occur in Sinapis alba and 

 Brassica nigra, are also found in other species of Sinapis and 

 Brassica, as well as in the following plants, but the oils produced 

 are not identical: Horseradish (Roripa Armoracea) , the oil being 

 similar to volatile oil of mustard; water cress {R. Nasturtium) ; 

 garden radish {Raphanus sativus) ; Sisymbrium Alliaria of 

 Europe, and the hedge mustard {S. officinale) naturalized in the 

 United States; turnip {Brassica rapa) of Europe; field penny- 

 cress (Thlaspi arvense) of Asia and found in waste places in the 

 Eastern and Middle United States ; the narrow leaved pepper- 

 grass (Lepidium rudcrale) naturalized from Europe; scurvy-grass 

 ( Cochlearia officinalis) of Northern and Middle Europe, the herb 

 of which, known as Herba cochleari^e, is used in medicine ; 

 " HONESTY " (Lunaria annua) common in cultivation on account 

 of the ornamental use of the dry pods ; Parrya macrocarpa of 

 Southern Europe; treacle mustard {Erysimum cheiranthoides) of 

 Northern Europe and the United States, and garlic mustard {E. 

 Alliaria). 



The seeds of most of the Cruciferse are also rich in fixed oils, 

 and the commercial oils are obtained from the following species : 



