As against the common belief out of 16 families showing C 4 type of photosynthesis ( in some of their plant species ) mainly found in tropical plants where initial carbon acceptor is Phospho enol pyruvate carboxylase and first stable product is Oxalic acid   acid Malate  , 15 families are of dicotyledonous plants and only one family of monocot i.e. Graminae has this type of photosynthesis. Only Euphorbiaceae has all the three types of photosynthesis in their plant spp.
Chenopodiaceae and Amaranthaceae are two important families having C 4 plants which are highly salt tolerant. They do not have typical Kranz anatomy of monocot plants but have spacial separation of enzymes of C3 and C 4 cycle. It would be of interest to know that C 4 plants first fix Carbon in C4 way in the cytoplasm of the mesophyll cells using Phosophoenol puryvate carboxylase enzymes and malate and oxaloacetate thus produced is decarboxylated in bundle sheath cells and Carbon dioxide thus released is fixed again using C3 cycle enzymes.
Amaranthus spp does this mechanism very well. This is the plant in growing in botanical garden of Justus Liebig Universitat Giessen.