A case of brittleheart has decimated the sycamore tree (Platanus occidentalis) shown on the right. Its trunk has been hollowed out by the action of fungi, putting it at risk of collapsing with the next bout of windy weather. The strange-looking tree shown below is the aptly named sack-of-potatoes or Socotran desert rose tree (Adenium obesum sokotranum), which is found on the Indian Ocean island of Socotra. Its swollen trunk stores essential water. Trees by Roland Ennos (Natural History Museum, London, £9.95, $14.95) explores the world of this most familiar group of living organisms.