MICHIGAN WEEDS. 



343 



MUSTARD FAMILY. CRUCIFERAE. 



Herbs with a pungent acrid juice (horse radish), sepals 4, petals usually 4, the upper portion spread- 

 ing in the form of a cross; stamens usually six, four longer than the other two, pod usually two-celled 

 by a very thin vertical partition. Seeds of many species become mucilaginous when soaked in water. 



There are about 1,500 species, most abundant in temperate regions. The family is easily recognized, 

 but the species are difficult to determine. 



Useful plants of the family are the cabbage, cauliflower, turnip, ruta baga, radish, rape, sweet alys- 

 sum, stock and a few others. Weeds in this family are abundant and aggressive, new ones arriving 

 one or more each year. It ranks as one of the prominent wesd-families. None is poisonous. 



Fig. 86 (78). 



Yellow or Small Alyssum. Alysmm 

 alyssoides L. A small annual, 10-25 cm. high, 

 appearing gray owing to immense numbers of 

 star-shaped hairs on the surface; leaves mostlv 

 spatulate, entire; flowers yellow: fruit flat, 

 nearly circular. Seldom prominent as a weed. 



Fig. 87 (79). 



Yellow Rocket. Winter Cress. Barbarea 

 vulgaris R. Br. (Barbarea Barbarea (L.) Mac. 

 M.) A smooth, erect, perennial, 30-60 cm. 

 high; lower leaves with petioles, the blade 

 lvrate-pinnatifid; flowers bright yellow, abun- 

 dant; pod obscurely four-angled. Introduced 

 from Europe. Rather frequent along ditches 

 and low land. Often sent in for name, but so 

 far not aggressive. 



