How can I find all all Transform or surf in one struct

I load a .mat-file in my script. This .mat-file is a struct (i.e. 'str') with data and objects. In my case I only want to find the objects (like Surface and Transform) and get the handles of them.

 str.a=2
 str.b=[1, 0.3, 0.5]
 str.c=mesh([1 1],[1 1],[0 1;0 1])
 str.d=struct('a',{mesh([1 1],[1 1],[2 1;2 1])},'b',{'test 1'})

and I want to find and save (I know there is no Transform but I want to find them too)

 str.c
 str.d.a

Is there an easy way that I can find all Surface and Transform in one struct?