When we integrate form, we feed in the tangent vector of the curve which maybe written as:
$$ \tau= \gamma'(t) dt$$
If we had a one form integral $\int dx$ if were to feed the above into the integral:
$$ \int_{\gamma} dx = \int_{t} dx(\gamma'(t) dt) = \int_t dt dx(\gamma'(t) )$$
Now, $dx(\gamma'(t) )$ is a number but is $dt$ again a one form or not? How do we differentiate between place holder for integration variable and one form?
Hopefully my question is clear. I was not sure how to best frame this