34 



OBJECT LESSONS IN BOTANY. 



45. A winged petiole is flattened horizontally. A sheath- 

 ing petiole embraces the stem with its winged edges like a 

 sheath. You can find plenty of examples of these forms. 



Fig. 83. Eose,— stipules adnate. Fig. 84. Violet ( V. tricolor), — gashed Mipnlcs. 



46. Let ns now study more particularly the varying forms 

 of the stipules. We have already defined them. (See Les- 

 son L, § 4.) Here is seen the leaf of a Kose and of a Pansy 

 (Figs. 83, 84), both with quite showy stipules. The former 



Fig. 85. Leaf of Conioselinum,— tri-pinnate, with sheathing petiole. 

 Fig. 86. Leaf of Polygonum Pennsylvanienm, with its (s) oehrea. 

 Fig. 87. Stem of Grass, with joint {j), leaf (Z), ligule (s). 

 Fig. 88. Leaf of Pear-tree, with slender stipules. 



45. What difference between a winged and compressed petiole ? Can you 

 describe a sheathing petiole? Give examples of these three forms. 



