15 



Stinkweed, Penny Cress. 



(Thlaspi arvense, L.) 



Though this weed is by no means new to the Province of Ontario, it 

 is worthy of attention here as it is being- constantly reported from new 

 sections of the Province. It seems to be spreading through the agency 

 of ground feed made from Western screenings and to some extent as 

 an impurity in farm seeds. It is considered to be one of the worst pests 

 of the grain fields of the West. Careful watch should be kept for it, as 

 it is a very free seeder, and the seeds are said to have great vitality and 

 to be able, like mustard seed, to remain in the ground for some years. 



Fig. 14. Seeds of Penny Cress . 



(Photo by Prof. M. V. Stingerland, Cornell Univ.) 



Enlarged about 12 times. 



Description. Stinkweed or Penny Cress is an annual or winter 

 annual belonging to the Mustard Family (Cruciferae). It is a foul smell- 

 ing plant from i to 2 feet high, bearing smooth, dark green, sessile 

 leaves, and clusters of small white flowers, which develop into orbicular 

 oods. These are flat, notched at the top, and about half an inch broad. 

 It is from these peculiarly shaped pods that the plant gets its common 

 name, Penny Cress. Each pod contains about a dozen seeds. The seeds 

 are about 1-14 of an inch long, flat, irregularly oval, bronzy brown to 

 metallic black in color, with regularly arranged curved lines on both sur- 

 faces. 



