PLATE 9. 



STINKWEED, Thlaspl arocnse, L. 

 Other English names: Penny-cress, French Weed. 

 (Noxious: Dom., Man., N.W.) 



Introduced. Annual and winter annual, with an abominable smell when 

 bruised. The most persistent and aggressive enemy of the western wheat 

 grower. Plants in bloom when winter sets in freeze up; but, as soon as they 

 thaw out in the spring, they continue to grow and mature their seed without 

 the slightest injury. The seeds of these early plants are ripe early in July. 

 Plants which grow from seed in the spring are not ripe until some weeks later. 

 Erect, stem simple or branching. Whole plant bright green and quite 

 smooth. Eoot leaves petioled; stem leaves spear-shaped, coarsely toothed, 

 clasping the stem at the arrow-shaped base. Flowers clear white, one-eighth 

 of an inch across. At first in a small flat cluster at the top of the leafy stem. 

 Kacemes elongated in fruit. Pods flat, f of an inch across, contain- 

 ing from 8 to 16 seeds, on slender upward-curved pedicels, pale green and 

 winged, notched at the top. Just before the seeds ripen, the pods turn 

 to a characteristic greenish orange shade, which is easily noticed in fields 

 when this weed is growing among crops. Seeds [Plate 53, fig. 6 natural 

 size and enlarged 8 times] deep purplish brown, asymmetrically oval in 

 outline, flattened, with rounded edges, about T '^ of an inch across, a 

 little longer than broad. The surface of the seed has on each face five or six 

 loop-like lines, which start at the basal scar or notch and run concentrically 

 around a central groove, which starts between the radicle and the seed leaves. 

 The seed is a beautiful object when examined under a magnifying glass. 

 It is also interesting from having the seed leaves, inside the seed, flat and 

 with the radicle lying along their edges on one side (accumbent). There is 

 no mucilage developed on these seeds when soaked in water. 



Time of Flowering : Throughout the season ; seed ripe from July to frost, 

 and after the middle of June too far advanced to be ploughed down without 

 danger. 



Propagation : By seeds. 



Occurrence : Stinkweed is now found in every province of Canada, but 

 it is nowhere such a terrible pest to the farmer as in Manitoba and the North- 

 west. It was introduced on to the prairies at the time of the first settlers, 

 and its worst occurrences to-day are along the lines of the old trails ; but it 

 is rapidly spreading into new districts. 



Injury: On account of the great loss due to the presence on land of this 

 noxious weed, it is of the utmost importance that everyone should know its 

 appearance, so as to destroy it whenever it shows itself in a new locality. 

 The North-west Government, through their Chief Weed Inspector, Mr. T. 

 N. Willing, have adopted the wise plan of publishing an accurate and easily 

 recognized coloured picture of this weed. This was not only issued in their 

 Bulletin No. 16, "Hints for the Grain Grower," by Mr. Willing; 

 but, in addition, a copy of it was put in every school in the Territories so 

 that teachers and students might become familiar with the appearance of 



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