I too had some difficulty finding information about the flowers and pollination/fertilization using typical botanical terms. Not sure why this information was so difficult to find, but I had to do some digging. The Jepson guide notes that the flowers are 'generally bisexual' and contain stamens and an ovary, so this tells you they have both male and female parts and should be self-fertile. This USDA site notes the flowers are 'perfect', so again confirming male and female parts and should be self-fertile. The Washington Native Plant Society notes that they are pollinated by butterflies and bees, and that the fruit is consumed by birds and mammals. I am not sure why one of the trees produced fruit and the other did not, it could be related to the flowers and pollination, age of the trees, stress, or predation. There could be a lot of factors affecting pollination and berry production. This WSU article on propagating the tree notes that "it is difficult to tell ahead of time which individual plant will produce a good fruit set. A tree, however, that has a particular kind of fruit set one year has the same fruit set year after year, or sometimes in alternate years" and that this may be stress related. It also notes that each fruit contains 8 or more seeds so you should be able to collect a lot of seeds from the one tree that is fruiting. Finally, the Forest Service website states "Pacific madrone is described as providing abundant fruit almost every year (23). On a good site in the Sierra Nevada from 1958 through 1977, however, bumper seed crops were produced in 2 years, light crops in 8 years, and little or no seed in 10 years." So again, berry and seed production appears to be unpredictable and influenced by various, largely unknown, factors. I hope that helps.