Re: DO STOMATES OCCUR ON THE UPPER & LOWER LEVEL OF MESOPHYTES & XERIPHYTES?

Xerophytes have a variety of adaptations to reduce transpiration including 
fewer stomata, sunken stomata, thick cuticle, hairs that shade the leaf (as in 
old man cactus that looks like it is covered by gray hair), leaves that have 
evolved into spines with photosynthesis in the stem (as in cacti), CAM 
(crassulacean acid metabolism) in which stomates only open at night to fix 
carbon dioxide, and thick, fleshy leaves with greatly reduced surface area and 
water storage. Some plants reduce water loss in dry conditions by shedding 
their leaves. Ephemerals survive dry conditions as seeds and germinate, flower 
and set seed during a few weeks when the soil is moist. 

Window plants of the Kalahari desert have fleshy leaves with transparent areas 
on top. The leaves can be buried in sand and light can still reach down into 
the buried leaf.

Having stomates on upper and lower leaf surface or just the lower surface does 
not seem to be an important distinction between mesophytes and xerophytes.   


References

College botany text such as 

Stern, K.R. 1991. Introductory Plant Biology. Dubuque, Iowa: Wm. C. Brown 

Cronquist, A. 1971. Introductory Botany. New York: Harper and Row.