EI.F.MKNTS OF STRUCTTTRM, POT \^ Y. 



77 



Fig. 127. 



• itctn. Soa^^ctimestLc edges of large 

 teeth are themselves finely serrated, 

 and ill that case the leaf is douhhj 

 serrate (Fig. 127). If the teeth 

 point outtviirds, that is, if the two 

 edges of each tooth are of 

 the same length, the leaf 

 is dentate, but if the teeth, 

 instead of being sharp, are rounded, the leaf is 

 crenate (Fig. 128). The term uain/ explains itself. 



113. Base. There are two or three peculiar pjg jog 

 modificatious of the bases of simple sessile leaves which 

 are of considerable imi)ortance in distinguishing plants. 

 Sometimes a i)air of lobes project backwards and cohere 

 /^ on the other side of the stem, so that the stem 

 appears to pass through the leaf. This is the 

 case in our common Bellwort, the leaves of 

 which are accordingly described as i>crfoliate 

 (Fig. 129). Sometimes two opposite sessile 

 leaves grow together at the base, and clasp the 

 stem, as in the upper leaves of Honeysuckle, 

 in the Triosteum, and in one of our species of 

 Eupatorium. Such leaves are said to be connate or con- 

 nate- perfoliate (Fig. 130). In one of our Everlastings 

 the margin of the leaf is con- 

 tinued on each side below the 



Fig. 120. 



Fig. .^o. / 



point of insertion, and the 1 



o^es f 



Fig. 131. 



grow fast to the sides 



V 



