In the plant, just as in man, the morphological polarity coincides with the biological. There is, on the one hand, the process of assimilation (photosynthesis), so characteristic of the leaf. Through this process matter passes over from the aeriform condition into that of numerous separate, characteristically structured solid bodies - the starch grains. Besides this kind of assimilation we have learnt to recognize a higher form which we called 'spiritual assimilation'. Here, a transition of substance from the domain of levity to that of gravity takes place even more strikingly than in ordinary (physical) assimilation (Chapter X).