1069. The fall of the leaf. 'All leaves,' Dr. Lindley observes, 'are originally contiguous with the stem. As they grow, an interruption of their tissue at their junction with the stem takes place, by which a more or less complete articulation is formed, sooner or later. The articulation between a leaf and the stem being completed, the tissue of the former becomes gradually incrusted by the foreign matter deposited by the sap in the process of secretion and digestion; and at last it is incapable of further action, when it dies. When the stem continues to increase in diameter, the dead leaf not increasing with it, the latter is eventually thrown off; and this is the fall of the leaf.' (Elem. of Bot. p. 50.)
