You can use a credit card or send a personal check to the ISS treasurer. If you want to pay by check, it needs to be payable in US dollars and made out to "The International Symbiosis Society".  Mail it to the ISS Treasurer at the address below:

P.O. Box 1848 (Biology)

401 Shoemaker Hall

University of Mississippi

University, MS 38677-1848, USA

Phone: +1-662-915-1731

e-mail: erik@olemiss.edu