sentences:  The latter type always had a long vowel (' "to put", ' "to grow", ' "to give"), while this restriction did not hold for vowel-initial roots (' "to eat", ' "to drive", ' "to smell").Laryngeal theory can explain this behaviour by reconstructing a laryngeal following the vowel (', , ', resulting in a long vowel) or preceding it (", , , resulting in a short vowel).These reconstructions obey the mentioned rules.