Sec. 18. Liability of person signing in trade or assumed name. - No person is liable on the instrument whose signature does not appear thereon,  except  as  herein  otherwise  expressly  provided.  But  one who signs in a trade or assumed name  will be liable to the same extent as if he had signed in his own name.
 
GENERAL RULE AS TO LIABILITY OF PERSON WHOSE SIGNATURE IS NOT ON INSTRUMENT

      A  person  whose  signature  doesn’t  appear  on  the  instrument  is  not liable 
 
EXCEPTIONS TO THE GENERAL RULE
1.    Where a duly authorized agent signs for a person, the person is liable
2.    Where a person sought to be charged forges the signature of another person, the forger is liable even if his signature doesn’t appear thereon
3.    Where a person sought to be charged signs on a paper separate from the  instrument  itself,  as  in  an  allonge,  although  the  allonge  may  be considered a part of the instrument, or where an acceptance is written on a paper other than the bill itself
4.    Where  the  person  uses  an  assumed  name  or  trade  name—one  may become  a  party  to  a  negotiable  instrument  by  any  designation  he desires