58 



THE LEAF 



the edges of the leaf curve inwards, making a little pouch 

 or stomach, and an acid juice exudes from the glands and 

 digests the meal. After a number of days, varying 

 according to the digestibility of the diet, the blades slowly 

 unfold again and are ready for another capture. 



In the bladderwort, common in pools and still waters 

 nearly everywhere, the petioles are transformed into floats, 

 while the finely dissected, rootlike blades bear little bladders 

 which, when examined under the microscope, are found to 

 contain the decomposed remains of captured animalculae. 



113. — Bladderwort, showing finely dissected submerged leaves bearing bladders, 

 and petioles transformed to a whorl of floats for buoying up the flowering stem. 



72. Protective Leaves. — One of the most frequent 

 modifications of leaves is for protection, either of them- 

 selves or of other organs, against animals, drought, exces- 

 sive moisture, dust, heat, cold, etc. The prickles of the 

 thistle and horse nettle, the hairs of the stinging nettle, 

 and the sharp spears from which the Spanish bayonet 

 ( Yucca aloifolia) takes its name, are all familiar examples 

 of the first kind, as are also the venom of the poison ivy, 



