76 



THE ROYAL SOCIETY OF CANADA 



Total cars examined 



Polygonum Convolvulus L 



Chenopodium album L 



Avena fatua L 



Neslia paniculata (L) Desv 



Saponaria Vaccaria L 



Brassica species 



Conringia orientalis (L) Dumort . 



Thlaspi arvense L 



Sisymbrium altissimum L 



Lappula echinata Gilibert 



Agrostemma Githago L 



Ambrosia trifida L 



Amaranthus retroflexus L 



Lepidium apetalum Willd 



Axyris amarantoides L 



Dracocephalum parviflorum Nutt 



Cirsium arvense (L) Scop 



Sonchus arvensis L 



Lolium temulentum L 



151 



150 



144 



46 



15 



59 



29 



91 



63 



61 



35 



3 



47 

 13 



7 

 3 

 2 



176 



175 



176 



81 



17 



14 



8 



69 



44 



47 



64 



It will be noticed that some kinds of weed seeds, notably wild 

 oats, lamb's quarters and wild buckwheat, seem to be of general 

 distribution, while others are more prevalent in some localities than 

 others. For example, ball mustard (Neslia paniculata (L.) Desv.) 

 occurred in forty-two cars out of seventy-one from Macdonald, Man., 

 while hare's-ear mustard (Conringia orientalis (L.) Dumort) was 

 found in only eight. In contrast to this only fifteen cars out of 151 

 from Moose Jaw, Sask., contained ball mustard, while hare's-ear 

 mustard occurred in ninety-one. Great ragweed (Ambrosia trifida L.), 

 Canada thistle (Cirsium arvense (L.) Scop.), Sow thistle (Sonchus 

 arvensis L.) and darnel (Lolium temulentum L.) appear to be of only 

 local distribution as yet. 



As the distribution of weeds is determined by a number of factors 

 — accidental introduction, soil and climatic conditions, rotation and 

 system of cropping, etc. — no effort is made to interpret the data here 

 presented. 



