A majority in number of the holders of title to land susceptible of irrigation from a common source and by the same system of works, including pumping from subsurface or other water, who are also the holders of title to a majority in value of the land may propose the formation of a district under the provisions of this division; or the formation of the district may be proposed by not less than 500 petitioners, each of whom is an elector residing in the proposed district or the holder of title to land therein and which petitioners include the holders of title to not less than 20 per cent in value of the land included within the proposed district.