La geometria intuitiva nella scuola media italiana del '900

The aim of the paper is to show on hand of the curricula and the textbooks for the lower gymnasium the idea of intuitive geometry that was growing up in Italy between the end of the 19th century and the beginning of the 20th century, in comparison with different interpretations in other countries. We compare, on some specific points, the first texts on intuitive geometry, those of Veronese and Frattini, and analyze in particular the use of proofs, of experimental checks, of geometric transformations,... The history of the curricula and the textbooks continues, observing how the latter shift towards a rationalization of the geometry for the level corresponding to what is now called middle school, till to the inversion of the trend due to Ugo Arnaldi and Emma Castelnuovo. In the conclusion the different points of view are taken up again and characterizations of intuitive geometry are proposed which are valid also nowadays.