Short answers, pulled from the story.
Elms are deciduous and semi-deciduous trees comprising the genus Ulmus in the family Ulmaceae. They belong to the urticalean rosid clade and are distantly related to cannabis, mulberries, figs, hops, and nettles.
A single pound of British elm seeds contains approximately 50,000 individual units. These seeds are known as samarae and are so light that they can travel vast distances on the wind.
The fungus Ophiostoma ulmi arrived in Europe from Asia in 1910. It was first described in the 1920s by Dutch botanists Bea Schwarz and Christina Johanna Buisman.
Elm wood has been valued for its interlocking grain and resistance to splitting, making it a material of choice for wagon-wheel hubs, chair seats, and coffins. The wood was also used for keels in ship construction and as water pipes during the medieval period in Europe.
The Liberty Tree was an American white elm in Boston, Massachusetts, in front of which the first resistance meetings were held against British attempts to tax the American colonists from 1765. When the British felled it in 1775, the Americans took to widespread Liberty Elm planting and sewed elm symbols on to their revolutionary flags.
Efforts to develop DED-resistant cultivars began in the Netherlands in 1928 and continued, uninterrupted by World War II, until 1992. Research has followed two paths involving species and species cultivars, and hybrid cultivars.