If you take a small plot of wild land, say 50'x50' and visit it everyday watching all the various mushrooms which will grow there (there will be far more then most people realize or expect) and try and find the sense in where and when they fruit it becomes difficult to write it all off as simple biological responses to environment/following the food/etc, and even if you do look at it that way and start adding up the possible causes and effects you can end up with such a long list that it becomes difficult to not see it as some sort of at least instinctual level intelligence and that the growth of mycelium often has more in common with crawling than mindless growth.
For example, many mushrooms are very good at fruiting just out of sight from trails, walk 20' off the trail, turn around and suddenly you start seeing mushrooms. Instinct is to say that all the mushrooms which grow within sight of the trail get picked by curious people or kicked by children but if you start looking for remains and stumps and mushrumps and those hard to spot just starting to fruit immature buttons, you find surprisingly few. So you think environmental, the trail alters windflow and runoff, animal movement, etc, but than you notice that this is true of even those small trails created by a fox or children which only affect a bit of low growing undergrowth so only has a tiny effect on a very localized area. On and on it goes until you run out of explanations.
I am mostly convinced there is some level of intelligence here and we just can not see it because it is so very different from what we understand as intelligence. But, I may just spend too much time with mushrooms, during the season I always seem to have at least a dozen various mushrooms which I will visit everyday to watch them grow and rot away.