Here for the curious is what this stem looked like two weeks ago:
So all the growth in the picture is new since then.
Ocotillos spend most of their time not growing, but when they do grow, the speed can be pretty amazing. The baby spines are still rubbery soft but the older ones in the picture are already hard enough to work for protection.
The two types of leaves which are characteristic of the genus (also including our native cirio or Boojum tree) are the spine leaves (the first leaves to emerge along a stem) which leave behind the lower part of the petiole to become a spine after they fall, and the axillary leaves without a petiole that appear in subsequent seasons whenever a stem releafs (also sometimes right after the other kind, as in the original photo). The second type of leaf is very clearly illustrated in this picture.
Now go back to the late July pic above and you can clearly distinguish some of the incoming spine leaves based on their petiole. For example the one at 8 o'clock, and its mirror at 4'oclock.
