I got some orchids for Christmas and all of them are in plastic pots which
are then placed in clay pots. My book says that clay should be used because
it's dries better then plastic. So, should I take all my plants out of the
clay pots then out of the plastic pots then replace them in the clay pot?

(clarify: right now the soil of my plant is in a plastic pot and then that
plastic pot is placed in a clay pot. So when you look at it from the side it
looks like the plants in clay but from the top you see that inside the clay
pot is a plastic pot which contains the roots and soil of the plant.)

Also if I have an Oncidium, Dendrobium, and Phal all in the southern window
of the house getting a nice dose of direct sunlight (at least for the ones
closest to the window which are Dendrobium and Oncidium) is my set up ok?
Also they are all planted in moss is that ok?

Finally, when my book refers to growth there talking about what? (I know
I've asked this before but I didn't understand how root can be monitored for
growth)

Thanks
Chris