LESSON 16.] THEIR ARRANGEMENT IN THE BUD. 109 



by making a horizontal slice of the flower-bud when just ready to 

 open ; and it may be expressed in diagrams, as in Fig. 223, 224. 



280. The pieces of the calyx or the corolla either overlap each 

 other in the bud, or they do not. When they do not, the aestivation 

 is commonly 



Valvate, as it is called when the pieces meet each other by their 

 abrupt edges without any infolding or overlapping ; as the calyx of 

 the Linden or Basswood (Fig. 223) and the Mallow, and the corolla 

 of the Grape, Virginia Creeper, &c. Or it may be 



Jnduplicate, which is valvate with the margins of each piece pro- 

 jecting inwards, or involute (like the leaf in Fig. 152), as in the 

 calyx of Virgin's-Bower and the corolla of the Potato, or else 



Reduplicate, like the last, but the margins projecting outwards 

 instead of inwards ; these last being mere vari- 

 ations of the valvate form. 



281. When the pieces overlap in the bud, it 

 is in one of two ways : either every piece has 

 one edge in and one edge out ; or some pieces 

 are wholly outside and others wholly inside. 

 In the first case the aestivation is 

 Convolute or twisted, as in the corolla of Geranium (most com- 

 monly, Fig. 224), Flax (Fig. 191), and of the Mallow Family. 

 Here one edge of every petal covers the next 

 before it, while its other edge is covered by 

 the next behind it. In the second case it is 



Imbricated or imbricate, or breaking joints, 

 like shingles on a roof, as in the calyx of Ge- 

 ranium (Fig. 224) and of Flax (Fig. 191), 

 and the corolla of the Linden (Fig. 223). In 

 these cases the parts are five in number ; and the regular way then 

 is (as in the calyx of the figures above cited) to have two pieces en- 

 tirely external (1 and 2), one (3) with one edge covered by the first, 

 while the other edge covers that of the adjacent one on the other 

 side, and two (4 and 5) wholly within, their margins at least being 

 covered by the rest. That is, they just represent a circle of five 

 leaves spirally arranged on the five-ranked or f plan (187, 188, 

 and Fig. 143-145), only with the stem shortened so as to bring 

 the parts close together. The spiral arrangement of the parts of 



FIG. 223. Section across the flower-bud of Linden. 



FIG. 234. Section across the riower-bud oi Geranium : the sepals numbered in their order 



10 



