Malus sieversii modern apple cultivars. Unlike domesticated varieties its leaves go red in autumn: 62.2% of the trees in the wild do this compared to only 2.8% of the regular apple plant or the 2,170 English cultivated varieties. The species is now considered vulnerable to extinction. "Malus sieversii" has previously been identified as the main contributor to the genome of the cultivated apple ("Malus pumila"), on the basis of morphological, molecular, and historical evidence. A DNA analysis in 2010 confirmed "M. sieversii" as the progenitor of the cultivated apple. A third species that has been thought to have made contributions to the
Étienne-Louis Malus index between the surface and the interior of the glass). It was not until 1815 that Sir David Brewster was able to experiment with higher quality glasses and correctly formulate what is known as Brewster's law. This law was later explained theoretically by Augustin Fresnel, as a special case of his Fresnel equations. Malus is probably best remembered for Malus's law, giving the resultant intensity, when a polariser is placed in the path of an incident beam. His name is one of the 72 names inscribed on the Eiffel tower. Étienne-Louis Malus Étienne-Louis Malus (; ; 23 July 1775 –