Heat Tolerance

I need some help understanding heat tolerant plants! 
I read in a book on propagation that cuttings of temperate plants find 10° to 20° C. (50° to 68° F.) favourable for growth and 30° to 40° C. (86° to 104° F.) stressful and lethal. My two to four week old cuttings of lavender, cistus, rosemary, sage, etc. in the shade on a drip line are doing fine. The temperatures have been over 90° F for weeks, yesterday at 112° F., 109° F. in the shade. That means that 104°  F. is not lethal to these heat tolerant plants. Does that mean that my cuttings have enough roots to keep up with their evapotransporation rate? What temperature is most favorable for growth a of cutting of a heat tolerant plant? When would be a good time to start more cuttings? At what temperature do Mediterranean plants go dormant? What causes a plant to go dormant in the heat? Does the plant look physically different when dormant? 
I will appreciate any information you can provide.

Kathleen     
Redding - the north end of California's Big Valley
Sunset zone 9   USDA zone 9
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