This is the so-called "Gourmet Salad". Close inspection reveals that it contains (at least) Lettuce, Rocket, Red Mustard, Mizuna, and Pak Choi. As you can see, the leaf-miners have found the Mizuna, but so far the other plants look unscathed. Unfortunately the Rocket has already begun to bolt, but that seems to happen a lot when it is crowded as it is here.
In the first photo above you can make out a pot of "official" Mesclun behind the seed-tray. This contains amongst other things Sorrel, Celery Leaf, Endive, Chicory and even some Carrots (for their leaves). Put some of each of all this lot together with some Landcress from elsewhere in the garden, and you get this:
I added those mixed leaves to some of my larger-leaved Iceberg-style lettuce ("Webbs Wonderful") and some Radicchio and it made a really special salad. It's maybe a pity I didn't photograph it...
In view of my commitment to Successional Sowing, here is the next lot of Mesclun, already on its way:
It looks a bit sparsely-populated, because despite the application of blue slug-pellets, the blessed slugs have still managed to penetrate the defences!
Growing salads in seed-trays and pots like this is a good way to do it when Winter is approaching, because you can easily move the plants under cover in a cold-frame or greenhouse if you need to.