Sentence:  "Your Silver Shoes will carry you over the desert," replied Glinda. "If you had known their power you could have gone back to your Aunt Em the very first day you came to this country." "But then I <WSD>should</WSD> not have had my wonderful brains!" cried the Scarecrow. "I might have passed my whole life in the farmer's cornfield." 
Meaning of the word marked with <WSD> tags:  A variant of would when used with first person subjects.