148 JOURNAL OF THE PLYMOUTH INSTITUTION. 
Sinapis alba), the one rare and the other common, are of medicinal 
value, are used as a small salad, and furnish the common table- 
mustard of commerce. The seeds of Sinap>is alba, now quoted at 
2 s. a gallon, produce about 36 per cent, of oil ; and those of 
Sinapis nigra about 18 per cent. This oil, produced after the 
seeds have been ground and pressed, is chiefly used in the manu- 
facture of soap. After the oil has been extracted, the cake of the 
seeds is powdered, mixed among other ingredients with 40 per 
cent, of wheaten flour, and becomes table-mustard. The French 
mustard has a blacker appearance than ours, and is more pungent, 
because in its preparation the husks are not removed. The Durham 
mustard is also darker in colour, and purer than the ordinary table- 
mustard. The mustards belong to the Cruciferous order of plants. 
To that order belong also our culinary vegetables — the cabbage, 
turnip, seakale, radish, cress, horse-radish. For the rotation of 
crops these are well-fitted, giving back to the soil what corn-plants, 
for instance, take out. 
Crambe maritima, Seakale, is absent from the Plymouth Flora. 
Cakile maritima, purple Sea-rocket, native, is common along the 
coast. This cruciferous plant, the sea-rocket, has qualities common 
to the order, and might be used as a vegetable. It is, however, not 
cultivated. Barbarea vulgaris — English common name Winter 
Cress, or Herb St. Barbara, or Yellow Rocket — native, and common 
in damp waste spots, is also fit for use as a vegetable, and in 
Sweden is eaten. Cows eat it ; but horses, goats, and sheep rarely 
touch it. It has a pungent and somewhat bitter taste. Si?ia]ns 
arvensis, common Charlock, very common, and too well known to 
farmers as a weed, is fit for use as a pot-herb ; and cattle and 
sheep are very fond of it. Brassica rapa, wild Turnip, is deemed 
to be a straggler from cultivation. 
Coming now to the Leguminiferous order of plants, mostly of great 
economic importance, we have the clovers, trefoils, vetches, peas, 
and beans. It also comprises Ulex europceus, common Furze, whin, 
or gorse, which, as we all know, we have in abundance. The 
wood being hard, white, and compact, is useful for ornamental 
inlaid woodwork, such as Tunbridge ware. It is also in the winter 
time an excellent fuel, especially for bakers' ovens. The young 
tender branches are a favourite food of sheep and other animals, 
for which object young furze is sometimes cultivated. 
Of the trefoils, many important as fodder, Ave have more species 
