#transverse section

For example, a transverse incision dividing the SAM from the primordium initial (I) caused the initial to develop radially without forming any adaxial tissue (Figure 19.3A). (...) However, two marginal incisions that allowed unimpeded communication between the SAM and the primordium initial led to the development of normal adaxial-abaxial symmetry (Figure 19.3B). (...) As described above, the abaxialized primordia produced by surgically isolating primordia from the apical meristem fail to form leaf blades (see Figure 19.3).