Ginn and Phillips championed the use of fibre needles made from bamboo, right from the beginning in ads for their 1924 Magnaphone. They started making their own in 1929. Their sale during the War kept EMG and EXPERT from going under. Esther Ginn is said to have made them by the thousand. They were sold in two shilling packs, the price of a pint of beer.
Bamboo needles were cut and then "doped" to dry and harden them. EXPERT sold Nucane, Brown & White fibre needles, presumably using different doping recipes
Thorn needles were made from all sorts of plant thorns from all over the world, some of these species may well now be extinct and some cactus plants are protected.
EXPERT thorn needles came in two sizes. One for normal acoustic soundboxes and miniature thorns for electric pickups
Here is an excellent web page on fibre needles and how to make your own.