Skandapurana 6.3.51.31

6.3.51.31

vārijaṃ saumyamāgneyaṃ vāyavyaṃ pārthivaṃ punaḥ .
vānaspatyaṃ bhavetṣaṣṭhaṃ prājāpatyaṃ tu saptamam .. 51.31 ..

The water-born, the gentle, the fiery, the airy, and again the earthy;
the arboreal is the sixth, and the Prajāpati-related is the seventh;