130 COMPOUND ORGANS OP PLANTS. 



These, although sometimes sessile, as in the rose and crowfoot, 

 have not ^infrequently their base tapering into a narrow stalk 

 analogous to the petiole of the leaf, which is called an unguis 

 or claw ; whilst their upper portion, which corresponds to the 

 blade of the leaf, is broader and more expanded, and is called 

 the lamina, as in the wall-flower. (Fig. 36.) Petals organized 

 in this manner are termed unguiculate. 



Fig. 36. 



Pig. 36. Cruciform corolla and unguiculate petal of the wall-flower, (Cheiranthus.) 



The following are some of the leading forms assumed by the 

 regular polypetalous corollas. The rosaceous, of which the rose 

 is the type, have spreading petals without claws or with very 

 short ones. The cruciform, in which there are four petals, 

 usually with claws, arranged in the form of a cross, as in the 

 wall-flower. The liliaceous, in which the petals, six in number, 

 gradually taper from the base to the apex, as in the lily. The 

 caryophyllaceous, where the petals have long, narrow, tapering 

 claws, which are enclosed in a tubular calyx, as in the pink. 



Irregularities in the form of polypetalous corollas may result 

 from the unequal development of the petals, as in the violet ; 

 but these are not sufficiently marked as to justify the appli- 

 cation of any particular term. There is, however, one form 



