Sift flour, measure and resift 3 times with baking powder, soda, and salt. Cream shortening and sugar until light and fluffy. Add eggs one at a time and beat well after each addition. Add bananas and mix. Add flour in 4 portions and beat until smooth after adding each portion. Add nuts, if desired, at this time. Turn into a well-greased pan (8" x 4" x 2 1/2") and bake in moderate oven, (350 degrees) for 50 minutes or until done. A cake tester inserted into bread comes out clean, or use a sharp table knife. Cool on rack. 1 loaf.