Colorado Weed SeeDvS 
47 
Key to SpeeieM 
Seeds smooth 
Seeds yellow 1..B. alba 
Seeds black 2 . .B. arvensis 
Seeds not smooth 
^Seeds marked with pits deeper than the network of fine 
lines surrounding them 2..B. nigra 
^Seeds marked with pits no deeper than the network of fine 
^ lines surrounding them 4..B. juncea 
^Seeds of B. nigra can also be distinguished from B. juncea by their smaller 
size and redder color. Seeds of B. juncea are usually covered with a grayish bloom 
which can be easily rubbed off. 
Fig, 72. White Mustard (Bras- 
sica alba), x 22. 
1. White Mustard (Bras- 
sica alha (L.) Boiss.) (Fig. 72). 
— Seeds dull, antimony-yellow in 
color, smooth, irregular in shape, 
mostly oblong to slightly flattened 
or nearly spherical, 2-2.5 mm. 
long. 
2. Wild Mustard, Charlock (Brassica arvc'nsi^ 
(L.) B. B. P.) (Fig. 73). — Seeds dull, slate-black to 
black in (olor, smooth, spherical in shape, 1-1. S mm. 
ill diameter. 
Fig. 73. Wild 
Mustard (Brassica 
arvensi.s). x 11. 
Fig. 74. Black Mus- 
tard (Brassica nigra). 
X 22. 
3. Black Mustard (Brassica nigra (L.) 
Koch.) (Fig. 74). — Seeds brick-red in color, 
rough, spherical in shape, 1-1.5 mm. in diamt 'er 
(usually noticeably smaller than either B. 
arvensis or B. juncea), surface marked with 
pits distinctly deeper than the network of fine 
lines bordering them. 
