32 



OBJECT LESSONS IN BOTANY 



Ficj. 76. Potentilla anserina; leaf with five cut lobes, almost qninate. 

 Fig. 77. Potentilla tridentata ; ternate, with palmate, three-toothed leaflets 

 Fig. 78. JefFersonia diphylla ; a binate leaf. 

 Fig. 79. Lemon ; a simple leaf jointed to the petiole. 



LESSON VIII. 



SESSILE LEAVES— FORMS OF STIPULES. 



41. Y\^E have alreaclj stated (Lesson L, § 5) that many 

 leaves are without petioles (foot-stalks), or, in other words, are 

 sessile. The figures presented on page 33 exhibit some of the 

 modes of attachment peculiar to sessile leaves. In Fig. 80 

 (an Aster) you see leaves of the form called spatulate (Lesson 

 III., § 5), having large base lobes nearly clasping the stem 

 at the point of attachment. Such leaves are said to be arrh- 

 plexicaul (stem -clasping). 



42. In the next figure (81, Bellwort) the leaves are ellipti- 

 cal, parallel-veined, and not only clasp the stem at base, but 

 the lobes there grow together on the opposite side, appearing 

 as if the stem passed through the leaf; that i^., perfoliate. 



40. What kind of venation have all these forms ? On the palmate vena- 

 tion what forms are founded ? 



41. When are leaves said to he sessile? Define an amplexicaul lea£ 



42. Can you define a perfoliate leaf? 



