The following cards without the ability word Landfall:
Courser of Kruphix; Nissa, Vastwood Seer; Primeval Bounty; Sporemound; Stone-Seeder Hierophant; Vinelasher Kudzu; Zendikar's Roil.
- I can't give you an official answer, but a few educated guess.
- Ability words are like flavor text. They add no function and are italic. Its most practical use is to search for gather.
- Landfall is a Zendikar mechanic, so only cards from the two Zendikar blocks use the landfall ability word.
- It is not uncommon that there are similar mechanics in exist in keyworded and non-keyworded form in magic, compare Ghostflame Sliver to Forerunner of Slaughter for example.
- I hope that clears things up. You can try to get an official answer at Blogatog - Yandere Sliver 12:08, 19 January 2016 (UTC)