Complex sentence: The leaves on long shoots are non-photosynthetic, developed into three-spined thorns long; the bud in the axil of each thorn-leaf then develops a short shoot with several normal, photosynthetic leaves.
Split into simpler sentences: The leaves on long shoots are non-photosynthetic, developed into one to three or more spines long. The bud in the axil of each thorn-leaf then develops a short shoot with several normal, photosynthetic leaves.