ADHESION 



51 



be continued into a terminal point. They may be concave, as in Theo- 

 broma (Fig. 71); the margin may be toothed and the apex toothed or 

 fimbriated, as in Silene (Fig. 72) ; the toothing of the margin may extend 

 into a pinnatifid condition, as in the calyx 

 lobe of Rosa canina (Fig. 73), and that of 

 a toothed or fimbriate apex into the cleft 

 or divided state of chorisis. 



The Pappus. — The peculiarly divided 

 calyx illustrated in Fig. 79, a, is denomi- 

 nated a Pappus, and this term has been 

 extended to all forms of the calyx (Figs. 

 74 to 83) existing in that family (the 

 Compositae) and in some others. Fig. 80 

 illustrates the action of median, as well as 

 of lateral chorisis, in the development of 

 a double pappus, the outer circle being 

 much shorter and different in kind. 



The several forms of perigone parts 

 corresponding to those of leaves (see leaf-forms) and numerous inter- 

 mediate ones not illustrated, should be carefully considered by the 

 student, as they have a most important bearing upon the forms of the 

 corolla produced by cohesion, which we shall shortly consider. 



r/ 



r£ 



7S. 



Fig. 71. Concave petal of Theobroma. 

 72. Flower of Silene, the petals toothed 

 at apex and bearing a crown at junction 

 of limb with claw; also a conspicuous 

 anthophore in base of calyx. 73. Pinna- 

 tifid sepal of Rosa. 



T.TS. 77. 



Figures illustrating forms of the pappus; Fig. 74 Pappus little changed from ordinary superior 

 calyx-limb. 75. That of Tanacctum, reduced to a short cup. 76. That of Absinthium, practically 

 obsolete. 77. That of Wyethia, 2 of the calyx-teeth awned. 78. That of Grindelia, the two remaining 

 calyx-teeth aristiform. 79. That of Arnica, the ordinary setose form. 80. The double pappus of 

 .Bnfleron, the outer series very short. 81. Plumose bristle from pappus of Z/asiopo(?on. 82. Scaly bristle 

 from pappus of Eriosphaera. 83. Serrate bristle from pappus of Cineraria. 



Adhesion. — Both adhesion and cohesion are exceedingly common in 

 the case of the perigone. The former has already been pretty fully 

 considered. Very rarely is it so complete that there is not at least a 

 portion of the parts remaining free. Since the adherent parts are 



