The law of demand implies that when the price of a good rises, people buy less of it. This makes the demand curve slope monotonically downwards. A textbook exception is the so-called Giffen good that by definition behaves in the opposite way.
But take a stock on the rise; might there not at least be one tendency for people to buy more of it under some circumstances, because it looks promising, in spite of any opposite tendencies? Is or isn't this another case where a demand curve may slope upwards?