110 ZSSSOJfS WITS PLANTS 



XX. THE ATTACHMENT OF THE LEAF, AND 

 THE "insertion OF THE PETIOLE 



119. Compare the manner in which the petiole 

 joins the stem (or shoot) in the apple (Fig. 2), 

 lilac (Fig. 8), maple (Figs. 13, 14), rhododendron 

 (Fig. 52), and quince (Fig. 53). It is essen- 

 tially the same in all of them. The end of the 

 petiole is slightly expanded, but the insertion (as 

 the mode of attachment is called) may be said 

 to be ordinary. 



120. Now compare the dahlia (Fig. 91). Here 

 the base of the petiole is dilated ; and it will 

 be observed that in this particular case the bases 

 of the two opposite petioles cohere, and this 

 may explain the ring-like leaf- scar of the dahlia 

 shown in Fig. 38. When two sessile , opposite 

 leaves cohere, they are said to be connate (Fig. 

 106). 



121. Sessile leaves have various methods of 

 attachment. Fig. 107 is the common mullein. The 

 edges of the leaf run down the stem, and such 

 leaves seldom fall away with a distinct and clean- 

 cut fracture or scar. This is a decurrent leaf. 

 The leaf may be clasping or amplexicaul (Fig. 

 108), the length of the basal lobes varying greatly. 

 Sometimes these lobes are long and ear -like, and 



