This is a plant with a simple declarative message: Go Away. Its razor sharp edges — I’m assuming they’re razor sharp — have the same function as cactus needles. I was tempted to call this a cactus at first, but my brief research suggests it is merely an aggressive succulent, in the sense that the best offense is a good defense. I took this picture from several feet away and cropped it to avoid the chance of losing my balance and reaching out to save myself. If I were a plant, I think I would concentrate on growing away from it. But it's magnificent. It’s three or four feet wide. It’s rugged and determined, and looks like it might eat passersby for a snack. I tend to walk on the far side of the sidewalk as I pass, and glance at it with due respect.