19 d please "prosthesis grafted in bodily tissue, such as an artificial tooth" (7) I***A*T
39 a "simple autotrophic organisms which lack true stems, roots or leaves such as seaweeds" (5) ****E
24 a "horse riding exercise consisting of a series of S-shaped figures in the schooling arena" (10) *****N*I*E. I even ride, so I ought to know that, but am stuck. Many thanks in optimistic advance!