Complex sentence: The spores are thick-walled, smooth, and spindle-shaped, with dimensions of 11--15 by 4--5 µm; larger spores up to 18 µm long may also be present.
Split into simpler sentences: The spores are thick-walled, smooth, and spindle-shaped, with dimensions of 11--15 by 4--5 µm. Larger spores up to 18 µm long may also be present.