Similar turgescence changes, taking place with similar rapidity in the midrib of the leaf of Dionaea, explainthe closing of the lobes upon their hinge.
Conditions of hyper-turgescence are common in herbaceous plants in wet seasons, or when overcrowded and in situations too moist for them.
But it also appears that honeydew may be excreted by ordinary processes of over-turgescence pressing the liquid through water-pores, as in the tropical Caesalpinia, Calliandra, &c. That these exudations on leaves should afterwards serve as pabulum for Fungie.g.
In dry-country grasses the blades are often folded on the midrib, or rolled up. The rolling is effected by bands of large wedge-shaped cells - motor-cells - between the nerves, the loss of turgescence by which, as the air dries, causes the blade to curl towards the face on which they occur.