172 NATURE STUDY AND AGRICULTURE 
22. Wild Mustard: Yellow Mustard. — This plant with 
its yellow blossoms is familiar to all. It is one of the most 
—_____________.___, troublesome weeds in our fields. Many 
farmers prevent it from getting a foot- 
hold upon their land by going through 
their grain fields every summer when it 
is in bloom and pulling all the plants. 
If this practice is begun before the 
weed is too common, the amount of 
labor required is not prohibitive. 
23. Tumbling Mustard. — The flow- 
ers of this mustard are pale yellow or 
nearly white and not so showy as in the 
preceding species, the pods are longer and more slender, 
and the seeds smaller. If allowed room for growth, the 
plant becomes very bushy, and in the fall the wind breaks 
it loose from the ground and rolls it over the fields, distrib- 
uting seeds along its path. It is 
one of the most abundant seed- 
producers known. A large plant 
may bear 1,500,000 seeds, and could 
seed down nearly 5 acres of ground 
giving 7 seeds to every square foot. 
24. French Weed: Penny Cress. 
— This may be recognized by its 
offensive odor, flat pods with a deep 
notch at the end, and its small 
white flowers. While most of the 
seeds do not germinate until spring, 
some of them come up in the fall, the young plants live 
through the winter, bloom early in the spring, and mature 
seeds soon after. It came to us from Europe by way of 
Witp Mustarp 
TumBLING MustarD 
