Maybe a typo for Spiranthes, which is an orchid? I can't find any reference to a Spiranthes hispidus, though.
I ran across this plant's description in a story by A.E.W. Mason, The House of the Arrow (copyright 1924, George H. Doran and Co.). In it, an elderly lady is dispatched by the crushed seeds of this plant which were then added to a drink. Natives of "the Kombe" region in Africa were described as mixing the seed-paste with clay, which was then smeared on arrows as poison. I will herewith transcribe the description of the plant, which Hanaud the detective reads from a large book, "a treatise printed by some learned society in Edinburgh": " 'This is the fruit of the plant Strophanthus Hispidus*, when it is ripening,' he said. The plate showed two long, tapering follicles joined together at their stems and then separating like a pair of compasses set at an acute angle. The backs of these follicles were rounded, dark in color and speckled; the inner surfaces, however, were flat, and the curious feature of them was that, from longitudinal crevices, a number of silky white feathers protruded. 'Each of these feathers,' Hanaud continued, 'is attached by a fine stalk to an elliptical pod, which is the seed, and when the fruit is quite ripe and these follicles have opened so that they make a straight line, the feathers are released and the wind spreads the seed. It is wonderful, eh? See!' Hanaud turned the pages until he came to another plate. Here a feather was represented in complete detachment from the follicle. It was outspread like a fan and was extraordinarily pretty and delicate in its texture; and from it by a stem as fine as a hair the seed hung like a jewel." *N.B.: In the above, quoted from Chapter VIII, the plant is referred to as Strophanthus Hispidus: however, in Chapter XV, the name is given as in my original post---Sporanthus Hispidus. ---If A.E.W. was still extant, I'd give him a piece of my mind on accuracy!!! Yes, I do realize that this is fiction, but it seemed such a detailed and specific description that I thought the plant just might be a real one. Thanks for responding, lorax!
Well, golly, it sure does help to have the CORRECT name!!! All sorts of info on Strophanthus---it is a member of the dogbane family: acts directly on heart muscle; slows pulse rate, and is a precursor of cortisone. Et voila!