A very similar painting in the National Gallery, London, is also ascribed to Leonardo da Vinci, and ascribed a date before 1508. Originally thought to have been partially painted by Leonardo's assistants, a close inspection of the painting during the recent restoration between 2008 and 2010 has led the conservators from the National Gallery to conclude that the greater part of the work is by the hand of Leonardo, but debate continues."The daffodil code: doubts revived over Leonardo’s Virgin of the Rocks in London", Dalya Alberge, The Guardian, 9 December 2014 Parts of the painting, the flowers in particular, indicate the collaboration and have led to speculation that the work is entirely by other hands, possibly Leonardo's assistant Giovanni Ambrogio de Predis and perhaps Evangelista.
