Very difficult to tell from B/W photos from this period in respect to the Gordon tartan as the yellow strip tended to be lost to the eye, though it looks to me either Black Watch or Argyll & Sutherland.
Looking closer at the the top of the kilt it looks as though he as a a non issue belt and the White Kilt lining is showing.
Full lengh puttees were worn at this period of the war with the short puttee's and hose being introduced over time., Hose were footless to reduce wear, an ordinary sock worn underneath for comfort, Diced hose in todays Highland Regiment are still footless, the price of hose bein very expensive.
I think I read somewhere that the Black Watch were the last Highland Regiment to phase out the long puttee during the Great War

Regards
Cef