110 AREANGEMENT OF PARTS IN THE BTJD. [lESSON 16. 



the blossom is the same as that of the foliage, — an additional evi- 

 dence that the flower is a sort of branch. The petals of the Linden, 

 with only one outside and one inside, as shown in Fig. 223, exhibit 

 a gradation between the imbricated and the convolute modes. When 

 the parts are four in number, generally two opposite ones overlap the 

 other two by both edges. When three in number, then one is outer- 

 most, the next has one edge out and the other covered, and the third 

 is within, heing covered by the other two; as in Fig. 190. This is 

 just the three-ranked r (J) spiral arrangement of leaves (186, and 

 Fig. 171). 



282. In the Mignonette, and some other flowers, the sestivation is 

 open; that is, the calyx and corolla are not closed at all over the 

 other parts of the flower, even in the young bud. 



283. When the calyx or the corolla is tubular, the shape of the 

 tube in the bud has sometimes to be considered, as well as the way 

 the lobes are arranged. For example, it may be 



Plaited or pKcate, that is, folded lengthwise ; and the plaits may 

 either be turned outwards, forming projecting ridges, as in the 

 corolla of Campanula ; or turned inwards, as in the corolla of the 

 Gentian, &c. When the plaits are wrapped round all in one direc- 

 tion, so as to cover one another in a convolute manner, the aestivation 

 is said to be 



Supervolute, as in the corolla of Stramoniimi (Fig. 225) and the 



Morning- Glory ; and ifl the Morning-Glory it is twisted besides. 



« 



FIG. 295. Upper part of the corolla of a Stramonium (Datura meteloides), in the bud. 

 Underneath is a cross-section of the same. 



