A HYBRID RAGWEED 
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A HYBRID RAGWEED. 
ROBERT BRADFORD WYLIE. 
During the summer of 1914 an unusual specimen of Am- 
brosia was noted which seems likely to have been a hybrid! The 
plant grew by the roadside on bottom land a few hundred yards 
from the Butler’s Landing bridge a couple of miles north of 
Iowa City. It stood near the foot of the long hill beyond the 
bridge and near the margin of the lowland. The location in the 
edge of the grading was favorable in that its soil received the 
wash from the higher land. The plant was surrounded by 
various weeds and among them and near by were several speci- 
mens of the supposed parent species, Am'hrosia trifida L., and 
Amhrosia artemisiifoMa L. 
Since much interest centers in hybrid forms, and further be- 
cause crosses between species of this genus are not common, a 
brief description should perhaps be given as a matter of record. 
The plant was first noted about the middle of July and was 
then so conspicuously different from the common ragweeds that 
the writer noticed it among the roadside vegetation while rid- 
ing along the highway. The location was marked by a ring of 
small stakes in the hope that it would escape the scythe. A 
mowing machine subsequently passed within a few inches but 
it was uninjured and grew undisturbed until autumn. Flowers 
were produced in abundance but no seeds were set, and so the 
story ended with the one plant. 
The plant grew to the height of about a meter — slightly 
taller than the surounding specimens of Ambrosia artemisiifolia. 
At the time of its discovery it was seemingly further along in 
its development than either of the supposed parent species. 
The stem was stoutish, branching freely at about 3 or 4 dm. 
from the ground, and was about 1.5 cm. in diameter at the 
base. The height of the plant was almost certainly retarded 
by a gall or distortion on the stem that seemed to involve most 
of its tissues 3 or 4 dm. above the ground and among the lower 
branches. There is a possibility, of course, that this wound, 
due perhaps to the sting of an insect, might have induced the 
abnormalities noted in the plant as a whole. But while such 
a wound might lead to vegetative peculiarities it would be less 
