Sentence:  Clearly , any line , l , of any bundle having one of these points of tangency , T , as vertex will be transformed into the entire pencil having the image of the second intersection of l and Q as vertex and lying in the plane <WSD>determined</WSD> by the image point and the generator of * * f which is tangent to \ g at T . 
Meaning of the word marked with <WSD> tags:  fix in scope; fix the boundaries of