460 



THE SMALL GRAINS 



cious, the male flower heads globe-shaped, 1 inch across, female heads 

 oblong and half as large. In large patches there may be found only 

 male flowers, showing that all came from a single seed. Seeds | 

 inch long, light brown, elongated-oblong, glabrous, somewhat flat- 



Fio. 144. Canada thistle. 



tened and curved, more or less bluntly angled, marked with faint 

 longitudinal lines ; the top nearly round, flat, having a narrow rim 

 with a small cone-shaped point in the center; pappus copious, 

 white. The pappus breaks off easily and is absent when the seeds 

 are found in commercial grain (Fig. 141 k). 



