Extra Slot [General]
REQ: Spellcaster level 4th+
You gain one extra spell slot in your daily allotment. This extra slot can be at any level up to one level lower than the highest-level spell you can cast. For example, a 4th level sorcerer gains either an extra 0 level or 1st level slot, allowing him to cast any known spell of the chosen level one more time each day. A 4th level wizard can prepare any extra 0 level or 1st level spell she knows. Once selected the extra spell slot never migrates up or down in level. Tome and Blood, pg 40.
REQ: Spellcaster level 4th+
You gain one extra spell slot in your daily allotment. This extra slot can be at any level up to one level lower than the highest-level spell you can cast. For example, a 4th level sorcerer gains either an extra 0 level or 1st level slot, allowing him to cast any known spell of the chosen level one more time each day. A 4th level wizard can prepare any extra 0 level or 1st level spell she knows. Once selected the extra spell slot never migrates up or down in level. Tome and Blood, pg 40.