The 1874 RLDS edition omitted the preposition of here in Jacob 5:19, but the 1908 RLDS edition restored it to the RLDS text. The of adds a partitive sense to the meaning. Here in Jacob 5 (the olive tree allegory), the direct object for the phrasal verb “lay up” does not usually take the partitive of:
Note, in particular, that for the last example listed above (in verse 71), Oliver Cowdery initially wrote “ye shall have joy in the fruit of which I shall lay up” but then almost immediately corrected the text by crossing out the of. Even so, the partitive of is found elsewhere in the olive tree allegory:
Thus the occurrence of of is possible, and it should be maintained in verse 19 and twice in verse 76 (but not in verse 71).
Summary: Retain the partitive of in Jacob 5:19 (“that I may lay up of the fruit thereof ”).