Hi,

There are two things you need to have in mind: The hair will not grow in areas where you don't have curves. The hair interpolation depends in several factors like the distance between roots, amount of curves/guides and interpolation settings. In the image I can't see your interpolation settings, I would recommend you to try affine interpolation, Manual triangulation and paint a distribution mask to determine where the hair should grow. Lastly, take a look into Hair From Guides documentation to learn more about hair interpolation and distribution. 

Documentation: 

https://ephere.com/plugins/autodesk/maya/ornatrix/docs/2/Hair_from_Guides.html